• dumping a lot of heat

    From john larkin@21:1/5 to All on Wed Dec 4 13:29:03 2024
    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to All on Wed Dec 4 16:55:50 2024
    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Yes. A toaster element: Nichrome wire woven onto a mica card in a
    perforated metal box.

    Already packaged, one can get ballast resistors for high-power VFDs
    used to power machine tools. The ballast resistor absorbs the energy
    stored in a large chuck spinning fast, when it's time to come to a
    stop quickly without over-voltage tripping the VFD.

    .<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Arie de Muijnck@21:1/5 to john larkin on Wed Dec 4 22:58:25 2024
    On 2024-12-04 22:29, john larkin wrote:
    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.


    I once used a 2kW grill element as a surge current limit resistor, mounted in top of the 19" cabinet.
    A thermal cutout (clixon) above it interrupted mains power (and issued an alarm) in case the shorting relay failed to close after 5 seconds.
    The idea was to charge up all PSU input caps for a 10kW power system before enabling the outputs. Worked fine.

    Arie

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Wed Dec 4 22:32:33 2024
    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Cooker hob ring?

    I once used three industrial fan heaters as the starting resistor for a
    large 3-phase motor with a big inertial load. They were wired in delta
    but connected to the star point of the motor - an arrangement which gave
    the required starting current and torque. After a predetermined time, a
    normal 3-phase contactor shorted them out and closed the star point,
    allowing the motor to run up to full speed. The system worked
    flawlessly, up to 8 times a day, for several years.

    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Rid@21:1/5 to john larkin on Wed Dec 4 18:53:31 2024
    john larkin <jl@glen--canyon.com> Wrote in message:r
    I'm thinking about building a biggish rackmount dummy load box. Itwould simulate series resistance and inductance. Part of the problemis that it will need to dump a lot of heat.We are using copper CPU coolers on PC boards, which are great up to acouple
    of hundred watts, but I'd like to do a kilowatt or two.https://highlandtechnology.com/Product/P945It would take a heap of expensive extruded heat sinks and fans to getrid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degCtemp rise.A small
    hair dryer can dump a kilowatt. So some sort of red-hotnichrome coils and a vicious fan might work.I'd prefer to not use water.I wonder if there is some sort of runs-red-hot power resistor.

    There are those Edison base ceramic heaters . Maybe you can cobble
    up something with those.

    Cheers
    --


    ----Android NewsGroup Reader---- https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to martin_riddle@verison.net on Wed Dec 4 21:06:27 2024
    On Wed, 4 Dec 2024 18:53:31 -0500 (EST), Martin Rid
    <martin_riddle@verison.net> wrote:

    john larkin <jl@glen--canyon.com> Wrote in message:r
    I'm thinking about building a biggish rackmount dummy load box. Itwould simulate series resistance and inductance. Part of the problemis that it will need to dump a lot of heat.We are using copper CPU coolers on PC boards, which are great up to
    acouple of hundred watts, but I'd like to do a kilowatt or two.https://highlandtechnology.com/Product/P945It would take a heap of expensive extruded heat sinks and fans to getrid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degCtemp rise.
    A small hair dryer can dump a kilowatt. So some sort of red-hotnichrome coils and a vicious fan might work.I'd prefer to not use water.I wonder if there is some sort of runs-red-hot power resistor.

    There are those Edison base ceramic heaters . Maybe you can cobble
    up something with those.

    Cheers

    Good idea.

    I recall the old screw-base ceramic cones, used in reflector-type
    space heaters.

    Maybe we could use the heaters that people use in ceramic firing
    kilns. I know that some people make their own kilns from fire bricks
    and some sort of heater bars.

    Yikes, this is 5400 watts!

    https://www.amazon.com/Beaquicy-Heating-Assembly-Thermostat-Resettable/dp/B083QFPSSC/

    or this

    https://www.amazon.com/PayandPack-Durablow-Fireplace-Replacement-compatible/dp/B00B8NY03G/


    About 0.2% of the price of buying "electronic" resistors.

    https://www.digikey.com/en/products/detail/vishay-sfernice/RWST40370CN1600JN/10729041

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to jl@glen--canyon.com on Thu Dec 5 07:18:31 2024
    On a sunny day (Wed, 04 Dec 2024 13:29:03 -0800) it happened john larkin <jl@glen--canyon.com> wrote in <lo51lj1da7a9ar0r9iavrcckuk00njsuoa@4ax.com>:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    I have an electric heater that blows out hot air.
    Cheap, reliable, available from many places, nice in winter.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Thu Dec 5 08:55:32 2024
    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best
    system is several spaced blackened steel baffle plates with vertical air passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth
    considering.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Thu Dec 5 08:07:35 2024
    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    HVAC heater elements are available, premounted in ductwork.

    Typical value 10R xKw. Tap, cut or series/parallel to your heart's
    content.

    The components to build similar structures, ceramic insulators,
    and terminals and coiled resistance wire (of selected tempco)
    are all available off the shelf. Punch your own metalwork.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to Liz Tuddenham on Thu Dec 5 08:01:01 2024
    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best
    system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth >considering.

    https://ve3ute.ca/2000a.html

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Thu Dec 5 06:03:23 2024
    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best
    system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).

    Seems to me that black baffles will absorb IR and get hot, so devolve
    to air-cooled heat sinks.

    The solution to the IR problem is to reduce the element temperature
    so's to shift the dissipation from radiation to air heat transfer. I
    think the math on that is good.

    I don't much mind if a user sees a dull red glow through the slots on
    the back of a rackmount box. Maybe we could add a cosmetic black
    baffle, but it can't be allowed to absorb much IR or it becomes the
    heat sink. Maybe a few percent would be OK.

    If I reflect the glow down, only very short people will see it.


    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth >considering.

    Probably not practical. Tubes are big and full of expensive vacuum
    which doesn't conduct heat well. May as well use some giant tubular incandescent lamp which has the same glass and heater as a big tube.
    Most are filled with a gas that conducts heat better than vacuum, so
    would bet more air cooling from the glass.

    Tubes radiate heat from the plate, so I'd need to step up my source to
    high voltage.

    Fun to think about.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to legg on Thu Dec 5 06:14:53 2024
    On Thu, 05 Dec 2024 08:01:01 -0500, legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best >>system is several spaced blackened steel baffle plates with vertical air >>passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth >>considering.

    https://ve3ute.ca/2000a.html

    RL

    If I'm going to use a finned circular heat sink, why put a tube
    inside? Resistors would be cheaper.

    But as noted, it would be hard to dump a kilowatt or two into a finned
    heat sink. Well, unless I let its surface temp approach incandescence.

    I'm considering using a class-D amplifier that can sometimes be
    back-driven as a dummy load, in which case it pumps up its own power
    supply, normally something like 70 volts maybe. I need to synthesize
    the equivalent of a two kilowatt, 75 volt zener.

    We're just brainstorming a product at this point, toying with goofy
    ideas. With the right people, that is as Phil says, the most fun you
    can have standing up.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to legg on Thu Dec 5 06:21:32 2024
    On Thu, 05 Dec 2024 08:07:35 -0500, legg <legg@nospam.magma.ca> wrote:

    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    HVAC heater elements are available, premounted in ductwork.

    Typical value 10R xKw. Tap, cut or series/parallel to your heart's
    content.

    Yeah, some commercial heating element would be great.


    The components to build similar structures, ceramic insulators,
    and terminals and coiled resistance wire (of selected tempco)
    are all available off the shelf. Punch your own metalwork.

    I'd rather not have to terminate the ends of a red-hot nichrome wire,
    if I can buy that already done.

    Electric clothes dryer elements look interesting. I'll look into duct
    heaters too; thanks for that tip.


    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Thu Dec 5 22:03:40 2024
    john larkin <JL@gct.com> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best >system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).

    Seems to me that black baffles will absorb IR and get hot, so devolve
    to air-cooled heat sinks.

    Yes, all the energy is eventually going to finish up heating the air,
    the only question is the pathway it takes. One way to avoid that would
    be to construct a massive infra-red searchlight beaming the energy away
    from the earth - or a broadcast transmitter beaming upwards.

    To dump heat into the air, you either have to have something very
    conductive with a large surface area or you need another way of
    spreading the energy across a suface, such as heat radiation. A big
    sheet of thin, blackened steel plate for heating by radiation is a lot
    cheaper than a thick die-cast aluminium lump with fins for heating by conduction.

    The economics of mechanically-forced air cooling are better than
    convection unless you are able to use a tall 'chimney', so that the
    energy of the waste heat is used to generate the draught.


    The solution to the IR problem is to reduce the element temperature
    so's to shift the dissipation from radiation to air heat transfer. I
    think the math on that is good.

    The economics aren't so good.if you have to spread the heat over a large
    area by conduction alone.


    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth >considering.

    Probably not practical. Tubes are big and full of expensive vacuum
    which doesn't conduct heat well. May as well use some giant tubular incandescent lamp which has the same glass and heater as a big tube.
    Most are filled with a gas that conducts heat better than vacuum, so
    would bet more air cooling from the glass.

    Tubes radiate heat from the plate, so I'd need to step up my source to
    high voltage.


    Yes, I did say 'rapidly-controllable'; if you just want a fixed
    resistor, a valve would be a highly uneconomical way of doing it.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to legg on Thu Dec 5 22:03:41 2024
    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best >system is several spaced blackened steel baffle plates with vertical air >passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth >considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic
    capacitors where they can get hot is just plain stupid. I have seen
    loads of shoddy radio/audio designs where the cathode resistor was
    strapped along the side of the bypass capacitor or the main smoother was
    stood up right next to the rectifier or the output valve.

    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From KevinJ93@21:1/5 to john larkin on Thu Dec 5 17:54:11 2024
    On 12/5/24 6:14 AM, john larkin wrote:
    On Thu, 05 Dec 2024 08:01:01 -0500, legg <legg@nospam.magma.ca> wrote:
    ...

    If I'm going to use a finned circular heat sink, why put a tube
    inside? Resistors would be cheaper.

    But as noted, it would be hard to dump a kilowatt or two into a finned
    heat sink. Well, unless I let its surface temp approach incandescence.

    I'm considering using a class-D amplifier that can sometimes be
    back-driven as a dummy load, in which case it pumps up its own power
    supply, normally something like 70 volts maybe. I need to synthesize
    the equivalent of a two kilowatt, 75 volt zener.

    We're just brainstorming a product at this point, toying with goofy
    ideas. With the right people, that is as Phil says, the most fun you
    can have standing up.


    You could do what large battery analysis equipment does and feed the
    energy back to the AC supply. Then you wouldn't have to dissipate the
    heat within your equipment.

    Grid-tied inverters for solar power are relatively low cost (< $1/Watt)
    and don't use large transformers so it shouldn't be too difficult,
    although there are probably lots of rules they would need to honour.

    kw

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Martin Rid@21:1/5 to john larkin on Thu Dec 5 22:18:47 2024
    john larkin <JL@gct.com> Wrote in message:r
    On Wed, 4 Dec 2024 18:53:31 -0500 (EST), Martin Rid<martin_riddle@verison.net> wrote:>john larkin <jl@glen--canyon.com> Wrote in message:r>> I'm thinking about building a biggish rackmount dummy load box. Itwould simulate series resistance and
    inductance. Part of the problemis that it will need to dump a lot of heat.We are using copper CPU coolers on PC boards, which are great up to acouple of hundred watts, but I'd like to do a kilowatt or two.https://highlandtechnology.com/Product/P945It
    would take a heap of expensive extruded heat sinks and fans to getrid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degCtemp rise.A small hair dryer can dump a kilowatt. So some sort of red-hotnichrome coils and a vicious fan might work.I'
    d prefer to not use water.I wonder if there is some sort of runs-red-hot power resistor.>>There are those Edison base ceramic heaters . Maybe you can cobble> up something with those. >>Cheers Good idea.I recall the old screw-base ceramic cones, used in
    reflector-typespace heaters.Maybe we could use the heaters that people use in ceramic firingkilns. I know that some people make their own kilns from fire bricksand some sort of heater bars.Yikes, this is 5400 watts!https://www.amazon.com/Beaquicy-Heating-
    Assembly-Thermostat-Resettable/dp/B083QFPSSC/or thishttps://www.amazon.com/PayandPack-Durablow-Fireplace-Replacement-compatible/dp/B00B8NY03G/About 0.2% of the price of buying "electronic" resistors.https://www.digikey.com/en/products/detail/vishay-
    sfernice/RWST40370CN1600JN/10729041

    No...

    This. https://www.processheating.com/products/air-load-bank/cone-h
    eaters/


    Cheers
    --


    ----Android NewsGroup Reader---- https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to John R Walliker on Fri Dec 6 08:29:33 2024
    John R Walliker <jrwalliker@gmail.com> wrote:

    On 05/12/2024 22:03, Liz Tuddenham wrote:
    john larkin <JL@gct.com> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem >>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>>> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors >>> just throw the problem elsewhere and eventually will tarnish, the best >>> system is several spaced blackened steel baffle plates with vertical air >>> passages between them (visual black is not always IR black).

    Seems to me that black baffles will absorb IR and get hot, so devolve
    to air-cooled heat sinks.

    Yes, all the energy is eventually going to finish up heating the air,
    the only question is the pathway it takes. One way to avoid that would
    be to construct a massive infra-red searchlight beaming the energy away from the earth - or a broadcast transmitter beaming upwards.

    To dump heat into the air, you either have to have something very conductive with a large surface area or you need another way of
    spreading the energy across a suface, such as heat radiation. A big
    sheet of thin, blackened steel plate for heating by radiation is a lot cheaper than a thick die-cast aluminium lump with fins for heating by conduction.

    The economics of mechanically-forced air cooling are better than
    convection unless you are able to use a tall 'chimney', so that the
    energy of the waste heat is used to generate the draught.

    A full sized rack cabinet could be remarkably similar to a chimney
    if it had baffles in the right places.

    Yes, as long as the ceiling of the room isn't lined with polystyrene
    tiles. It might not be very good for the air conditioning system in the building where this is installed, regardless of which dissipation method
    is used.

    In the days of germainium transistors, one firm used to make cabinets
    with a 'clerestory' roof, like an upturned tray suppoted on spacing
    pillars above the ventilation holes in the roof proper. This allowed
    the heated air to flow out under the lip in case some idiot put the
    instruction manual on the top of the cabinet.

    Another possibility, especially if there aren't going to be many of
    these on sale and the installation will be done by the firm that makes
    them, is to make a hole in the wall and stick some stainless-steel
    boiler flues up the outside of the building. Even better, in an old
    building. use a redundant fireplace and put the contol box in a
    decorative housing on the mantlepiece.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Fri Dec 6 06:23:19 2024
    On Fri, 6 Dec 2024 08:29:33 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    John R Walliker <jrwalliker@gmail.com> wrote:

    On 05/12/2024 22:03, Liz Tuddenham wrote:
    john larkin <JL@gct.com> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >> >>>> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >> >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >> >>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors >> >>> just throw the problem elsewhere and eventually will tarnish, the best >> >>> system is several spaced blackened steel baffle plates with vertical air >> >>> passages between them (visual black is not always IR black).

    Seems to me that black baffles will absorb IR and get hot, so devolve
    to air-cooled heat sinks.

    Yes, all the energy is eventually going to finish up heating the air,
    the only question is the pathway it takes. One way to avoid that would
    be to construct a massive infra-red searchlight beaming the energy away
    from the earth - or a broadcast transmitter beaming upwards.

    To dump heat into the air, you either have to have something very
    conductive with a large surface area or you need another way of
    spreading the energy across a suface, such as heat radiation. A big
    sheet of thin, blackened steel plate for heating by radiation is a lot
    cheaper than a thick die-cast aluminium lump with fins for heating by
    conduction.

    The economics of mechanically-forced air cooling are better than
    convection unless you are able to use a tall 'chimney', so that the
    energy of the waste heat is used to generate the draught.

    A full sized rack cabinet could be remarkably similar to a chimney
    if it had baffles in the right places.

    Yes, as long as the ceiling of the room isn't lined with polystyrene
    tiles. It might not be very good for the air conditioning system in the >building where this is installed, regardless of which dissipation method
    is used.

    In the days of germainium transistors, one firm used to make cabinets
    with a 'clerestory' roof, like an upturned tray suppoted on spacing
    pillars above the ventilation holes in the roof proper. This allowed
    the heated air to flow out under the lip in case some idiot put the >instruction manual on the top of the cabinet.

    Another possibility, especially if there aren't going to be many of
    these on sale and the installation will be done by the firm that makes
    them, is to make a hole in the wall and stick some stainless-steel
    boiler flues up the outside of the building. Even better, in an old >building. use a redundant fireplace and put the contol box in a
    decorative housing on the mantlepiece.

    We have in mind some commercial rackmount products, 1U to maybe 5U
    dummy loads that people would buy and bolt into their 19" racks like
    any other instrument. They would blow hot air out the back, like most
    other gear.

    My users typically have cold forced air enter a rack from below and
    expect it to exit near the top. I have one customer that controls the
    air temp to milliKelvins, in what may be the world's biggest clean
    room.

    https://lasers.llnl.gov/multimedia/photo-gallery?tid%5B%5D=401&tid%5B%5D=402&

    One rack that I know of is 2/3 full with kilowatts of Tek scopes and
    ARBs. Things you need youngsters to help lift. I insisted that my
    boxes be mounted BELOW the hot Tek stuff.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Lasse Langwadt@21:1/5 to Joe Gwinn on Fri Dec 6 17:56:05 2024
    On 12/4/24 22:55, Joe Gwinn wrote:
    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Yes. A toaster element: Nichrome wire woven onto a mica card in a
    perforated metal box.

    Already packaged, one can get ballast resistors for high-power VFDs
    used to power machine tools. The ballast resistor absorbs the energy
    stored in a large chuck spinning fast, when it's time to come to a
    stop quickly without over-voltage tripping the VFD.

    .<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>

    Joe Gwinn


    https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Fri Dec 6 17:40:38 2024
    john larkin <JL@gct.com> wrote:

    On Fri, 6 Dec 2024 08:29:33 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    John R Walliker <jrwalliker@gmail.com> wrote:

    On 05/12/2024 22:03, Liz Tuddenham wrote:
    john larkin <JL@gct.com> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem >> >>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >> >>>> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >> >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to
    keep the radiant heat away from the outer walls of the cabinet.
    Reflectors just throw the problem elsewhere and eventually will
    tarnish, the best system is several spaced blackened steel baffle
    plates with vertical air passages between them (visual black is not
    always IR black).

    Seems to me that black baffles will absorb IR and get hot, so devolve >> >> to air-cooled heat sinks.

    Yes, all the energy is eventually going to finish up heating the air,
    the only question is the pathway it takes. One way to avoid that would >> > be to construct a massive infra-red searchlight beaming the energy away >> > from the earth - or a broadcast transmitter beaming upwards.

    To dump heat into the air, you either have to have something very
    conductive with a large surface area or you need another way of
    spreading the energy across a suface, such as heat radiation. A big
    sheet of thin, blackened steel plate for heating by radiation is a lot >> > cheaper than a thick die-cast aluminium lump with fins for heating by
    conduction.

    The economics of mechanically-forced air cooling are better than
    convection unless you are able to use a tall 'chimney', so that the
    energy of the waste heat is used to generate the draught.

    A full sized rack cabinet could be remarkably similar to a chimney
    if it had baffles in the right places.

    Yes, as long as the ceiling of the room isn't lined with polystyrene
    tiles. It might not be very good for the air conditioning system in the >building where this is installed, regardless of which dissipation method
    is used.

    In the days of germainium transistors, one firm used to make cabinets
    with a 'clerestory' roof, like an upturned tray suppoted on spacing
    pillars above the ventilation holes in the roof proper. This allowed
    the heated air to flow out under the lip in case some idiot put the >instruction manual on the top of the cabinet.

    Another possibility, especially if there aren't going to be many of
    these on sale and the installation will be done by the firm that makes >them, is to make a hole in the wall and stick some stainless-steel
    boiler flues up the outside of the building. Even better, in an old >building. use a redundant fireplace and put the contol box in a
    decorative housing on the mantlepiece.

    We have in mind some commercial rackmount products, 1U to maybe 5U
    dummy loads that people would buy and bolt into their 19" racks like
    any other instrument. They would blow hot air out the back, like most
    other gear.


    You are going to need an awful lot of air if the exit temperature isn't
    to be too high. Ordinary domestic fan heaters seem to be the best
    starting point and some models would fit comfortably as a side-by-side
    pair into a 5U 19" rack dissipating about 3kW each. Any more than about
    1kW per Unit height is going to produce a dangerous temperature rise or
    need a noisy high-speed blower to cool it.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to Lasse Langwadt on Fri Dec 6 16:23:04 2024
    On Fri, 6 Dec 2024 17:56:05 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 12/4/24 22:55, Joe Gwinn wrote:
    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Yes. A toaster element: Nichrome wire woven onto a mica card in a
    perforated metal box.

    Already packaged, one can get ballast resistors for high-power VFDs
    used to power machine tools. The ballast resistor absorbs the energy
    stored in a large chuck spinning fast, when it's time to come to a
    stop quickly without over-voltage tripping the VFD.

    .<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>

    Joe Gwinn


    <https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/>

    Yeah, small shops often do this kind of thing. Cheap, and works just
    fine. Probably the original brake resistor had failed.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Lasse Langwadt@21:1/5 to Joe Gwinn on Sat Dec 7 03:58:13 2024
    On 12/6/24 22:23, Joe Gwinn wrote:
    On Fri, 6 Dec 2024 17:56:05 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 12/4/24 22:55, Joe Gwinn wrote:
    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Yes. A toaster element: Nichrome wire woven onto a mica card in a
    perforated metal box.

    Already packaged, one can get ballast resistors for high-power VFDs
    used to power machine tools. The ballast resistor absorbs the energy
    stored in a large chuck spinning fast, when it's time to come to a
    stop quickly without over-voltage tripping the VFD.

    .<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>

    Joe Gwinn


    <https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/>

    Yeah, small shops often do this kind of thing. Cheap, and works just
    fine. Probably the original brake resistor had failed.


    afaiu it came like that from the factory

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Fri Dec 6 20:53:17 2024
    On Fri, 6 Dec 2024 17:40:38 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Fri, 6 Dec 2024 08:29:33 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    John R Walliker <jrwalliker@gmail.com> wrote:

    On 05/12/2024 22:03, Liz Tuddenham wrote:
    john larkin <JL@gct.com> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It >> >> >>>> would simulate series resistance and inductance. Part of the problem >> >> >>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to
    keep the radiant heat away from the outer walls of the cabinet.
    Reflectors just throw the problem elsewhere and eventually will
    tarnish, the best system is several spaced blackened steel baffle
    plates with vertical air passages between them (visual black is not >> >> >>> always IR black).

    Seems to me that black baffles will absorb IR and get hot, so devolve >> >> >> to air-cooled heat sinks.

    Yes, all the energy is eventually going to finish up heating the air, >> >> > the only question is the pathway it takes. One way to avoid that would >> >> > be to construct a massive infra-red searchlight beaming the energy away >> >> > from the earth - or a broadcast transmitter beaming upwards.

    To dump heat into the air, you either have to have something very
    conductive with a large surface area or you need another way of
    spreading the energy across a suface, such as heat radiation. A big
    sheet of thin, blackened steel plate for heating by radiation is a lot >> >> > cheaper than a thick die-cast aluminium lump with fins for heating by >> >> > conduction.

    The economics of mechanically-forced air cooling are better than
    convection unless you are able to use a tall 'chimney', so that the
    energy of the waste heat is used to generate the draught.

    A full sized rack cabinet could be remarkably similar to a chimney
    if it had baffles in the right places.

    Yes, as long as the ceiling of the room isn't lined with polystyrene
    tiles. It might not be very good for the air conditioning system in the
    building where this is installed, regardless of which dissipation method
    is used.

    In the days of germainium transistors, one firm used to make cabinets
    with a 'clerestory' roof, like an upturned tray suppoted on spacing
    pillars above the ventilation holes in the roof proper. This allowed
    the heated air to flow out under the lip in case some idiot put the
    instruction manual on the top of the cabinet.

    Another possibility, especially if there aren't going to be many of
    these on sale and the installation will be done by the firm that makes
    them, is to make a hole in the wall and stick some stainless-steel
    boiler flues up the outside of the building. Even better, in an old
    building. use a redundant fireplace and put the contol box in a
    decorative housing on the mantlepiece.

    We have in mind some commercial rackmount products, 1U to maybe 5U
    dummy loads that people would buy and bolt into their 19" racks like
    any other instrument. They would blow hot air out the back, like most
    other gear.


    You are going to need an awful lot of air if the exit temperature isn't
    to be too high. Ordinary domestic fan heaters seem to be the best
    starting point and some models would fit comfortably as a side-by-side
    pair into a 5U 19" rack dissipating about 3kW each. Any more than about
    1kW per Unit height is going to produce a dangerous temperature rise or
    need a noisy high-speed blower to cool it.

    Yeah, about a kilowatt per U sounds about right.

    I was just running a Dynatron copper CPU cooler at about 300 watts,
    and the exit air was painful. I might spec 250 on that one, which
    would be uncomfortable but not dangerous.

    https://www.dropbox.com/scl/fi/bbotoirgcm3g5bsgo4b9i/20241206_145219.jpg?rlkey=yvvs6y09ggzz8h78qv980iitt&raw=1

    Incidentally, cooler specs seem to assume specific CPU power
    dissipation which correlates weakly to characterizing the cooler as a
    general heat sink.

    One could put a bunch of kilowatt-class mosfets on a couple of those
    coolers and make a monster class-D amp.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to JL@gct.com on Sat Dec 7 05:50:10 2024
    On a sunny day (Fri, 06 Dec 2024 06:23:19 -0800) it happened john larkin <JL@gct.com> wrote in <sg16lj5atqibsg0b51pdgph71u2ha4ck6i@4ax.com>:

    On Fri, 6 Dec 2024 08:29:33 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    John R Walliker <jrwalliker@gmail.com> wrote:

    On 05/12/2024 22:03, Liz Tuddenham wrote:
    john larkin <JL@gct.com> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem >>> >>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>> >>>> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>> >>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>> >>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep >>> >>> the radiant heat away from the outer walls of the cabinet. Reflectors >>> >>> just throw the problem elsewhere and eventually will tarnish, the best >>> >>> system is several spaced blackened steel baffle plates with vertical air
    passages between them (visual black is not always IR black).

    Seems to me that black baffles will absorb IR and get hot, so devolve >>> >> to air-cooled heat sinks.

    Yes, all the energy is eventually going to finish up heating the air,
    the only question is the pathway it takes. One way to avoid that would >>> > be to construct a massive infra-red searchlight beaming the energy away >>> > from the earth - or a broadcast transmitter beaming upwards.

    To dump heat into the air, you either have to have something very
    conductive with a large surface area or you need another way of
    spreading the energy across a suface, such as heat radiation. A big
    sheet of thin, blackened steel plate for heating by radiation is a lot >>> > cheaper than a thick die-cast aluminium lump with fins for heating by
    conduction.

    The economics of mechanically-forced air cooling are better than
    convection unless you are able to use a tall 'chimney', so that the
    energy of the waste heat is used to generate the draught.

    A full sized rack cabinet could be remarkably similar to a chimney
    if it had baffles in the right places.

    Yes, as long as the ceiling of the room isn't lined with polystyrene
    tiles. It might not be very good for the air conditioning system in the >>building where this is installed, regardless of which dissipation method
    is used.

    In the days of germainium transistors, one firm used to make cabinets
    with a 'clerestory' roof, like an upturned tray suppoted on spacing
    pillars above the ventilation holes in the roof proper. This allowed
    the heated air to flow out under the lip in case some idiot put the >>instruction manual on the top of the cabinet.

    Another possibility, especially if there aren't going to be many of
    these on sale and the installation will be done by the firm that makes >>them, is to make a hole in the wall and stick some stainless-steel
    boiler flues up the outside of the building. Even better, in an old >>building. use a redundant fireplace and put the contol box in a
    decorative housing on the mantlepiece.

    We have in mind some commercial rackmount products, 1U to maybe 5U
    dummy loads that people would buy and bolt into their 19" racks like
    any other instrument. They would blow hot air out the back, like most
    other gear.

    My users typically have cold forced air enter a rack from below and
    expect it to exit near the top. I have one customer that controls the
    air temp to milliKelvins, in what may be the world's biggest clean
    room.

    https://lasers.llnl.gov/multimedia/photo-gallery?tid%5B%5D=401&tid%5B%5D=402&

    One rack that I know of is 2/3 full with kilowatts of Tek scopes and
    ARBs. Things you need youngsters to help lift. I insisted that my
    boxes be mounted BELOW the hot Tek stuff.

    In the TV studios, plus all the technical control rooms,
    many kW say from spotlights, lighting and all technical equiment
    was dealt with by a huge airco system,

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to Liz Tuddenham on Sat Dec 7 11:49:14 2024
    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best
    system is several spaced blackened steel baffle plates with vertical air
    passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth
    considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic >capacitors where they can get hot is just plain stupid. I have seen
    loads of shoddy radio/audio designs where the cathode resistor was
    strapped along the side of the bypass capacitor or the main smoother was >stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to legg on Sat Dec 7 09:06:20 2024
    On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>> >> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>> >> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep
    the radiant heat away from the outer walls of the cabinet. Reflectors
    just throw the problem elsewhere and eventually will tarnish, the best
    system is several spaced blackened steel baffle plates with vertical air >>> >passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at >>> >a much higher temperature than transistors, so they might be worth
    considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic >>capacitors where they can get hot is just plain stupid. I have seen
    loads of shoddy radio/audio designs where the cathode resistor was
    strapped along the side of the bypass capacitor or the main smoother was >>stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    Tubes were awful. Still are.

    It's astounding that people built computers with tubes. Some had
    hardware floating point!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Sat Dec 7 09:43:27 2024
    On Sat, 7 Dec 2024 17:24:49 -0000 (UTC), Hul Tytus <ht@panix.com>
    wrote:

    I have used some 2 watt resistors that showed about 600 degf by
    iron/constantan but a red glow within could be seen by eye. Well above
    stated limits of 2 watts. Can't remember the name they went by
    but they were'nt wound types.
    The aluminum housed resisters are handy. 50 watt types have
    done much duty here.

    Hul


    I had a case where there was a powerup surge, and it destroyed the big
    Mil-type alum case resistors. They generally opened and shorted to the
    case.

    The Welwyn thick-film porcelain-on-steel things worked great, bolted
    to the chassis.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Hul Tytus@21:1/5 to john larkin on Sat Dec 7 17:24:49 2024
    I have used some 2 watt resistors that showed about 600 degf by iron/constantan but a red glow within could be seen by eye. Well above
    stated limits of 2 watts. Can't remember the name they went by
    but they were'nt wound types.
    The aluminum housed resisters are handy. 50 watt types have
    done much duty here.

    Hul


    john larkin <jl@glen--canyon.com> wrote:
    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Klaus Vestergaard Kragelund@21:1/5 to john larkin on Sun Dec 8 00:19:37 2024
    On 04-12-2024 22:29, john larkin wrote:
    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    I have thought many times, but never got around to make an electronic
    load with many parallel circuits. At JLCPCB the mounting cost is low, so
    no biggie

    The idea is to spread the heat out, not relying on one element, but
    many. Imagine a big PCB, like A3 size, spread out with 100 equal
    circuits electronic loads. Frequency response would be high, power
    dumping high also. Use a aluminum PCB like those used for LED lamps to
    get even lower Rth

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to klauskvik@hotmail.com on Sat Dec 7 17:44:34 2024
    On Sun, 8 Dec 2024 00:19:37 +0100, Klaus Vestergaard Kragelund <klauskvik@hotmail.com> wrote:

    On 04-12-2024 22:29, john larkin wrote:
    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    I have thought many times, but never got around to make an electronic
    load with many parallel circuits. At JLCPCB the mounting cost is low, so
    no biggie

    The idea is to spread the heat out, not relying on one element, but
    many. Imagine a big PCB, like A3 size, spread out with 100 equal
    circuits electronic loads. Frequency response would be high, power
    dumping high also. Use a aluminum PCB like those used for LED lamps to
    get even lower Rth

    Needs a fan too, somewhere.

    A CPU cooler is cheap and has a fan. It is a bit klunky to mount on a
    PCB.

    There are some nice heat-sinkable resistors. My TO-220s are cheap;
    I'll TDR one and see how fast it is.

    People make crazy high power aluminum nitride microstrip RF resistors
    too.

    I tested a Caddock DPAK surface-mount thick film resistor and it was
    pretty good. I'd expect the cheaper flat Ohmites or Riedons to be
    similar, likely better. I should TDR some.

    https://www.dropbox.com/scl/fo/9ms2pdlhiqhhkuk6daviz/ADejWZO8YqocNAzyZD6i9cs?rlkey=j6y6vexfkpzmbyn36it0tjm9b&dl=0

    It would be interesting to make a microstrip on one of those LED-type
    aluminum boards. The white dielectric looks very thin.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to john larkin on Sun Dec 8 07:43:42 2024
    On Sat, 07 Dec 2024 09:06:20 -0800, john larkin <JL@gct.com> wrote:

    On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem >>>> >> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>>> >> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> >> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep >>>> >the radiant heat away from the outer walls of the cabinet. Reflectors >>>> >just throw the problem elsewhere and eventually will tarnish, the best >>>> >system is several spaced blackened steel baffle plates with vertical air >>>> >passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at >>>> >a much higher temperature than transistors, so they might be worth
    considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic >>>capacitors where they can get hot is just plain stupid. I have seen >>>loads of shoddy radio/audio designs where the cathode resistor was >>>strapped along the side of the bypass capacitor or the main smoother was >>>stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    Tubes were awful. Still are.

    It's astounding that people built computers with tubes. Some had
    hardware floating point!

    Fly by wire in the Avro Arrow. . . .

    http://ve3ute.ca/query/G-Limiting_Computer.zip

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Sun Dec 8 13:33:39 2024
    john larkin <JL@gct.com> wrote:

    On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem >>> >> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>> >> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>> >> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep >>> >the radiant heat away from the outer walls of the cabinet. Reflectors >>> >just throw the problem elsewhere and eventually will tarnish, the best >>> >system is several spaced blackened steel baffle plates with vertical air >>> >passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at >>> >a much higher temperature than transistors, so they might be worth
    considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic >>capacitors where they can get hot is just plain stupid. I have seen >>loads of shoddy radio/audio designs where the cathode resistor was >>strapped along the side of the bypass capacitor or the main smoother was >>stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just
    poor transistors, they have a different lifestyle altogether. They also
    have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    2) Dissipating energy in a smaller space at higher temperatures.

    3) Easier to make with few exotic materials or processes.

    4) EMP-proof and radiation-proof in the event of nuclear war.

    Those properties aren't needed most of the time but when they are,
    valves are a lot easier to design with than transistors if you are
    conversant and comfortable with the technology. There are still very
    few single transistors that can out-perform a humble EF91 from the
    1940s.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Liz Tuddenham on Sun Dec 8 14:15:54 2024
    Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
    john larkin <JL@gct.com> wrote:

    On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It >>>>>>> would simulate series resistance and inductance. Part of the problem >>>>>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>>>>>> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>>>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>>>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep >>>>>> the radiant heat away from the outer walls of the cabinet. Reflectors >>>>>> just throw the problem elsewhere and eventually will tarnish, the best >>>>>> system is several spaced blackened steel baffle plates with vertical air >>>>>> passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at >>>>>> a much higher temperature than transistors, so they might be worth >>>>>> considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic
    capacitors where they can get hot is just plain stupid. I have seen
    loads of shoddy radio/audio designs where the cathode resistor was
    strapped along the side of the bypass capacitor or the main smoother was >>>> stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just
    poor transistors, they have a different lifestyle altogether. They also
    have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    2) Dissipating energy in a smaller space at higher temperatures.

    3) Easier to make with few exotic materials or processes.

    4) EMP-proof and radiation-proof in the event of nuclear war.

    Those properties aren't needed most of the time but when they are,
    valves are a lot easier to design with than transistors if you are
    conversant and comfortable with the technology. There are still very
    few single transistors that can out-perform a humble EF91 from the
    1940s.



    <nearly dies laughing>

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Sun Dec 8 07:47:25 2024
    On Sun, 8 Dec 2024 14:15:54 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
    john larkin <JL@gct.com> wrote:

    On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid >>>>>> (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It >>>>>>>> would simulate series resistance and inductance. Part of the problem >>>>>>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>>>>>>> couple of hundred watts, but I'd like to do a kilowatt or two. >>>>>>>>
    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>>>>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>>>>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot >>>>>>>> nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep >>>>>>> the radiant heat away from the outer walls of the cabinet. Reflectors >>>>>>> just throw the problem elsewhere and eventually will tarnish, the best >>>>>>> system is several spaced blackened steel baffle plates with vertical air
    passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at >>>>>>> a much higher temperature than transistors, so they might be worth >>>>>>> considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic >>>>> capacitors where they can get hot is just plain stupid. I have seen >>>>> loads of shoddy radio/audio designs where the cathode resistor was
    strapped along the side of the bypass capacitor or the main smoother was >>>>> stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just
    poor transistors, they have a different lifestyle altogether. They also
    have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    2) Dissipating energy in a smaller space at higher temperatures.

    3) Easier to make with few exotic materials or processes.

    4) EMP-proof and radiation-proof in the event of nuclear war.

    Those properties aren't needed most of the time but when they are,
    valves are a lot easier to design with than transistors if you are
    conversant and comfortable with the technology. There are still very
    few single transistors that can out-perform a humble EF91 from the
    1940s.



    <nearly dies laughing>

    Yup. EF91 is known as "Not the valve that won the war."

    Pentodes are *noisy*, at least 10 times more than some 3 cent jfet.

    There are a couple of high-voltage tubes that were, until recently,
    worth at least considering. But multi-KV fets are more sensible these
    days.

    I used to use the 1B3 HV rectifier diode as an amp, with the filament
    voltage modulating the conductivity. The downsides were the bandwidth
    and the X-ray hazard.

    One could make an optocoupled tube half-bridge, or full-bridge, with
    maybe a 30 KV supply. I guess you'd use batteries for filament power.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to Liz Tuddenham on Sun Dec 8 15:28:31 2024
    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem >> >>> >> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >> >>> >> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >> >>> >> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    If you are using elements at near red heat, remember you need to keep >> >>> >the radiant heat away from the outer walls of the cabinet. Reflectors >> >>> >just throw the problem elsewhere and eventually will tarnish, the best >> >>> >system is several spaced blackened steel baffle plates with vertical air
    passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at >> >>> >a much higher temperature than transistors, so they might be worth
    considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic
    capacitors where they can get hot is just plain stupid. I have seen
    loads of shoddy radio/audio designs where the cathode resistor was
    strapped along the side of the bypass capacitor or the main smoother was >> >>stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just
    poor transistors, they have a different lifestyle altogether. They also
    have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.


    2) Dissipating energy in a smaller space at higher temperatures.

    Dissipating a lot of heat with the heater without any net output.
    So low efficiency by default.


    3) Easier to make with few exotic materials or processes.

    https://www.google.com/search?make+your+own+transistor


    4) EMP-proof and radiation-proof in the event of nuclear war.

    Depends.
    The glass may easily break of the impact shock.


    Tubes need high voltages to work usually..
    I can run a JFET on 10 mV or so
    https://panteltje.nl/pub/lighting_a_LED_with_a_candle_IMG_3604.GIF
    than transform the voltage up.
    Useful when the grid is down in nuculear war

    Tubes had strong aging, studio equipment using tubes needed re-calibration all the time.



    Those properties aren't needed most of the time but when they are,
    valves are a lot easier to design with than transistors if you are
    conversant and comfortable with the technology. There are still very
    few single transistors that can out-perform a humble EF91 from the
    1940s.

    Lots can be done and have been done with dual gate MOSFETs

    LIfetime of transistors is way better than tubes, especially in power applicatioin like for example TVs
    and related equipment.

    That said, my 1979 Trio oscilloscope's CRT still works (used it yesterday)
    But it is a transistor scope.
    Color CRT transistoir based monitor in the attic likely works too, have not tried it in years

    Fluorescent toobs work too, have some for above the workbench upstairs

    But the LED bulbs are nice, some are better.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Sun Dec 8 16:23:26 2024
    john larkin <JL@gct.com> wrote:

    Yup. EF91 is known as "Not the valve that won the war."

    That's because it wasn't available until 1947. :-)


    One could make an optocoupled tube half-bridge, or full-bridge, with
    maybe a 30 KV supply. I guess you'd use batteries for filament power.

    Not necessarily. The Cockroft-Walton multipliers made by Philips, for generating high-energy X-rays, superimposed RF on the capacitor chain
    and derived the heater current from that. (It's somewhere in the
    Philips Technical Review but I can't remember where.)


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to Jan Panteltje on Sun Dec 8 16:36:25 2024
    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just >poor transistors, they have a different lifestyle altogether. They also >have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Sun Dec 8 09:09:58 2024
    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just
    poor transistors, they have a different lifestyle altogether. They also
    have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
    and 30 kilowatts for 25 uSec.

    No vacuum tube can survive 1000 amps because no vacuum tube can
    conduct 1000 amps.

    A thyratron or an ignitron can conduct 1000 amps.

    A krytron is even better.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Sun Dec 8 17:34:56 2024
    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just >> >poor transistors, they have a different lifestyle altogether. They also >> >have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the >triodes in an ECC91. It drew about 100 mA for a few seconds with no >damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to >about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
    and 30 kilowatts for 25 uSec.

    Into the gate?

    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Sun Dec 8 10:38:02 2024
    On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just >> >> >poor transistors, they have a different lifestyle altogether. They also >> >> >have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
    and 30 kilowatts for 25 uSec.

    Into the gate?

    Don't do that.

    It's not hard to protect a mosfet from failure. The only way to
    protect a tube from failure is to not use it.

    A 1B3 makes a nice high-voltage capacitor, which is very reliable.

    I have some beautiful tubes. 833 transmit jug. Some Blue Arcturus
    things. A krytron. Some acorn and prox fuse tubes. A few gorgeous CRTs
    and PMTs.

    https://www.dropbox.com/scl/fo/m2ff4ty142v65omvmqf9k/ADvXu5nmmZ06w2hLulkZYL8?rlkey=z2tncdtgojshzogufp59xgxtw&dl=0

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to Lasse Langwadt on Sun Dec 8 13:27:51 2024
    On Sat, 7 Dec 2024 03:58:13 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 12/6/24 22:23, Joe Gwinn wrote:
    On Fri, 6 Dec 2024 17:56:05 +0100, Lasse Langwadt <llc@fonz.dk> wrote:

    On 12/4/24 22:55, Joe Gwinn wrote:
    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem >>>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>>>> couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Yes. A toaster element: Nichrome wire woven onto a mica card in a
    perforated metal box.

    Already packaged, one can get ballast resistors for high-power VFDs
    used to power machine tools. The ballast resistor absorbs the energy
    stored in a large chuck spinning fast, when it's time to come to a
    stop quickly without over-voltage tripping the VFD.

    .<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>

    Joe Gwinn


    <https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/>

    Yeah, small shops often do this kind of thing. Cheap, and works just
    fine. Probably the original brake resistor had failed.


    afaiu it came like that from the factory

    So no doubt it's properly mounted. Hard to beat electric stove
    elements on ruggedness and price.

    Joe Gwinn

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Sun Dec 8 21:08:42 2024
    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't
    just poor transistors, they have a different lifestyle altogether.
    They also have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to >> >about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
    and 30 kilowatts for 25 uSec.

    Into the gate?

    Don't do that.

    ...but that is the comparison with what I did by accident. I did it to
    a device that was designed as an RF amplifier with a rated dissipation
    of less than 3 watts and you were comparing it with a semiconductor that
    was massively bigger - and now you say don't do that - and the device
    needs extra protection components.

    That was the point I was making: you can get away with mishaps in a
    valve circuit that you can't get away with in a comparable transistor
    circuit.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to john larkin on Sun Dec 8 20:29:11 2024
    john larkin <JL@gct.com> wrote:
    On Sun, 8 Dec 2024 14:15:54 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
    john larkin <JL@gct.com> wrote:

    On Sat, 07 Dec 2024 11:49:14 -0500, legg <legg@nospam.magma.ca> wrote: >>>>
    On Thu, 5 Dec 2024 22:03:41 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    legg <legg@nospam.magma.ca> wrote:

    On Thu, 5 Dec 2024 08:55:32 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It >>>>>>>>> would simulate series resistance and inductance. Part of the problem >>>>>>>>> is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a >>>>>>>>> couple of hundred watts, but I'd like to do a kilowatt or two. >>>>>>>>>
    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get >>>>>>>>> rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot >>>>>>>>> nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor. >>>>>>>>
    If you are using elements at near red heat, remember you need to keep >>>>>>>> the radiant heat away from the outer walls of the cabinet. Reflectors >>>>>>>> just throw the problem elsewhere and eventually will tarnish, the best >>>>>>>> system is several spaced blackened steel baffle plates with vertical air
    passages between them (visual black is not always IR black).

    If you need a rapidly-controllable load, valves can dissipate energy at
    a much higher temperature than transistors, so they might be worth >>>>>>>> considering.

    https://ve3ute.ca/2000a.html

    Most of my valve designs err on the safe side. Putting electrolytic >>>>>> capacitors where they can get hot is just plain stupid. I have seen >>>>>> loads of shoddy radio/audio designs where the cathode resistor was >>>>>> strapped along the side of the bypass capacitor or the main smoother was >>>>>> stood up right next to the rectifier or the output valve.

    By standard 'safe' design, tubes have a pretty limited life.

    By 1956, the heater was no longer the weakest element in
    the life equation for these parts - glass electrolysis was.

    Electrolytic caps and their use has always been an issue.
    Cuffing the tubes not only enforces distance to other
    components, but reduces radiant effects in the viscinity.

    Win, win.

    RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just >>> poor transistors, they have a different lifestyle altogether. They also >>> have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    2) Dissipating energy in a smaller space at higher temperatures.

    3) Easier to make with few exotic materials or processes.

    4) EMP-proof and radiation-proof in the event of nuclear war.

    Those properties aren't needed most of the time but when they are,
    valves are a lot easier to design with than transistors if you are
    conversant and comfortable with the technology. There are still very
    few single transistors that can out-perform a humble EF91 from the
    1940s.



    <nearly dies laughing>

    Yup. EF91 is known as "Not the valve that won the war."

    Pentodes are *noisy*, at least 10 times more than some 3 cent jfet.

    There are a couple of high-voltage tubes that were, until recently,
    worth at least considering. But multi-KV fets are more sensible these
    days.

    I used to use the 1B3 HV rectifier diode as an amp, with the filament
    voltage modulating the conductivity. The downsides were the bandwidth
    and the X-ray hazard.

    One could make an optocoupled tube half-bridge, or full-bridge, with
    maybe a 30 KV supply. I guess you'd use batteries for filament power.



    The last time I designed a tube into a circuit was around 1990, to drive a sensing grid in an air ionization measurement. It was an 811A, and was able
    to drive the grid to -500V (with respect to the other grids) in a
    microsecond or so, and then get completely out of the way of the charge measurement.

    Tubes are still unequaled for that sort of thing—high voltage, high impedance, very low volume.

    They stink for everything else, even apart from being big, inconvenient, power-hungry, and expensive.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Sun Dec 8 14:48:16 2024
    On Sun, 8 Dec 2024 21:08:42 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't >> >> >> >just poor transistors, they have a different lifestyle altogether.
    They also have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of >> >> >the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to >> >> >about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
    and 30 kilowatts for 25 uSec.

    Into the gate?

    Don't do that.

    ...but that is the comparison with what I did by accident. I did it to
    a device that was designed as an RF amplifier with a rated dissipation
    of less than 3 watts and you were comparing it with a semiconductor that
    was massively bigger - and now you say don't do that - and the device
    needs extra protection components.

    That was the point I was making: you can get away with mishaps in a
    valve circuit that you can't get away with in a comparable transistor >circuit.

    My first job interview, I told the guy that I preferred tubes to
    transistors because it was harder to blow up tubes. He sniffed and
    said "That won't do" and dismissed me.

    I said the same thing in my next interview. Melvin laughed and hired
    me and I designed about $200 million worth of stuff for him.

    This was back when I got tubes for free or nearly free, and a PNP
    germanium transistor cost two weeks allowance.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Sun Dec 8 18:04:10 2024
    On Wed, 4 Dec 2024 22:32:33 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Cooker hob ring?


    What's that in American ??!!


    I once used three industrial fan heaters as the starting resistor for a
    large 3-phase motor with a big inertial load. They were wired in delta
    but connected to the star point of the motor - an arrangement which gave
    the required starting current and torque. After a predetermined time, a >normal 3-phase contactor shorted them out and closed the star point,
    allowing the motor to run up to full speed. The system worked
    flawlessly, up to 8 times a day, for several years.

    This looks like junk

    https://www.amazon.com/dp/B00B8NY03G?ref=ppx_yo2ov_dt_b_fed_asin_title

    but the price is right. I didn't understand it, so I got one, and I
    still don't understand it.

    The heater element has four faston lugs: one common, two resistors
    each 22 ohms to common, one n/c.

    The wires and thermal link are mysteries to me.

    But something like this with a squirrel-cage blower behind it would be
    slick. (or a hedgehog or a platypus blower.)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to Liz Tuddenham on Mon Dec 9 06:25:29 2024
    On a sunny day (Sun, 8 Dec 2024 16:36:25 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r499nc.1l79pftrqcriyN%liz@poppyrecords.invalid.invalid>:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just
    poor transistors, they have a different lifestyle altogether. They also
    have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    The 100 mA is a current limit due to the limited electron emission possible from that cathode
    at those settings.
    You can get flash-over with anode voltage at the grid of toobs.
    I understand you love toobs, sure toobs were nice
    some arguments against using those:
    1) glowball worming,
    2) slow startup time of your system
    3) bad efficiency, heater needs power all the time
    4) fragile
    5) toobs are BIG, imagine your smartphone electronics done with tubes,
    it would take a whole room or even building, and a special power station to power it..
    if you could get it working at all.
    6) weight
    7) sockets, bad contacts toobs thrown out of sockets
    8) CRTs versus LCDs or OLEDs? smartphone with a color CRT?
    9) touch screen????
    10) X-Ray emission from the monitor HV stabilizer tubes..
    etc etc
    I have designed with toobs
    In the early sixties in school I got hold of an old tube based CRT TV, round CRT tube at that time.
    Then 'teletor' appeared in a Dutch magazine, all transistor TV with scope CRT as screen.
    I modified it to drive that real old magnetic deflection TV set with transistors
    HV tronsformer, the works.
    Was an interesting learning curve...
    Never longed back to toobs after that.
    Had to work with those up into the late seventies every day in the studios. plumbicans, vidicons, CRT monitors full of tubes... racks full of tubes, video recorders...
    CRT based Tectronics scopes everywhere...
    35 mm film scanners with tubes, all the sync stuff, audio stuff,
    Transistors slowly made their way, Ampex AVR1 as the most complicated all transistor I worked on.

    Toobs are pretty much dead... for consumer producs.
    Imagine drone electronics, may as well get a 747 to carry the power pack...
    GPS receiver with toobs?
    LOL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to JL@gct.com on Mon Dec 9 06:36:13 2024
    On a sunny day (Sun, 08 Dec 2024 10:38:02 -0800) it happened john larkin <JL@gct.com> wrote in <sfpblj1ckqupo92hh5vtvnbds9g9k655ii@4ax.com>:

    On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just
    poor transistors, they have a different lifestyle altogether. They also
    have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to >>> >about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
    and 30 kilowatts for 25 uSec.

    Into the gate?

    Don't do that.

    It's not hard to protect a mosfet from failure. The only way to
    protect a tube from failure is to not use it.

    A 1B3 makes a nice high-voltage capacitor, which is very reliable.

    I have some beautiful tubes. 833 transmit jug. Some Blue Arcturus
    things. A krytron. Some acorn and prox fuse tubes. A few gorgeous CRTs
    and PMTs.

    https://www.dropbox.com/scl/fo/m2ff4ty142v65omvmqf9k/ADvXu5nmmZ06w2hLulkZYL8?rlkey=z2tncdtgojshzogufp59xgxtw&dl=0

    Yes I still use PMTs in my gamma spectrometers.
    https://panteltje.nl/pub/PMT/PMT_1_img_2435.jpg
    no heater so efficient!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to john larkin on Mon Dec 9 09:33:35 2024
    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 21:08:42 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't >> >> >> >just poor transistors, they have a different lifestyle altogether. >> >> >> >They also have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of >> >> >the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the >> >> >triodes in an ECC91. It drew about 100 mA for a few seconds with no >> >> >damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
    and 30 kilowatts for 25 uSec.

    Into the gate?

    Don't do that.

    ...but that is the comparison with what I did by accident. I did it to
    a device that was designed as an RF amplifier with a rated dissipation
    of less than 3 watts and you were comparing it with a semiconductor that >was massively bigger - and now you say don't do that - and the device
    needs extra protection components.

    That was the point I was making: you can get away with mishaps in a
    valve circuit that you can't get away with in a comparable transistor >circuit.

    My first job interview, I told the guy that I preferred tubes to
    transistors because it was harder to blow up tubes. He sniffed and
    said "That won't do" and dismissed me.

    I was asked the same question at my first job interview. I just said I understood valves better, which was true at the time. The Chief
    Engineer, who was interviewing me, then produced the circuit diagram of
    one of the firm's valve communications receivers and asked me to go
    through it and tell him what each part did.

    I took one look at it and said "Yuck! It's chassis-live". My
    interviewer let me continue and then gave me the job. It turned out
    later that he hated having to make the set that way but for commercial
    reasons it had to work on 110v D.C. and therefore had to have the
    chassis connected to one pole of the mains. (The chassis was well
    insulated from the casing and all the outside fittings and connections.)

    Throughout the entire job with that firm, I never had to design with
    valves - but I did ten years later when I had to make some high voltage research equipment.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to Jan Panteltje on Mon Dec 9 09:33:36 2024
    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 16:36:25 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r499nc.1l79pftrqcriyN%liz@poppyrecords.invalid.invalid>:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just >> >poor transistors, they have a different lifestyle altogether. They also >> >have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the >triodes in an ECC91. It drew about 100 mA for a few seconds with no >damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to >about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    The 100 mA is a current limit due to the limited electron emission
    possible from that cathode at those settings. You can get flash-over with anode voltage at the grid of toobs.

    There was a 1k current-limiting resistor in the HT supply (it changed
    colour). At least I had time to get to the 'off' switch before the
    valve could be seriously damaged. Luckily I was testing with reduced HT
    (about 100v) so the current would have been limited to about 100mA by
    the resistor, even if the maximum emission had been greater


    I understand you love toobs, sure toobs were nice

    I enjoy designing with them, rather than just copying well-worn
    circuits. There are still niches to be explored.

    A few years ago I set myself the task of designing a low-noise audio
    preamp using a grounded-grid first stage - the result was far better
    than I had expected because it had repercussions on the second stage and
    the mixing stage which greatly improved the overload performance and the
    S/N ratio of the whole amplifier. If I had invented that in the 1950s,
    I would be a lot richer now.

    I sent copies of the 'before' and 'after' circuits to a friend who is a
    great believer in the mystical properties of valves, but is otherwise
    quite sensible. It took him two days to get his mind around how the
    circuit actually worked.


    [...]
    9) touch screen????

    I have never needed a touch screen. The only time I have used them is
    at supermarkets and that was for their convenience, not mine.


    10) X-Ray emission from the monitor HV stabilizer tubes..

    Grossly over-hyped.


    [...]
    I modified it to drive that real old magnetic deflection TV set with transistors HV tronsformer, the works. Was an interesting learning
    curve... Never longed back to toobs after that.

    My first experience with transistors was building a simple automatic
    parking light for a car from a circuit in a magazine. It used a photoconductive cell to switch a chain of ever-larger transistors and
    supply a 12v bulb. The idiot who 'designed' it had added negative
    feedback instead of positive feedback, so the bulb never went right out
    and never came full on. The heatsink got hot and it ran down the car
    battery in daylight.

    It took a long time after that before I felt happy with transistors.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to Liz Tuddenham on Mon Dec 9 11:25:24 2024
    On a sunny day (Mon, 9 Dec 2024 09:33:36 +0000) it happened liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in <1r4ajzg.1c6xbb41kswk38N%liz@poppyrecords.invalid.invalid>:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 16:36:25 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r499nc.1l79pftrqcriyN%liz@poppyrecords.invalid.invalid>:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't just >> >> >poor transistors, they have a different lifestyle altogether. They also >> >> >have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the
    triodes in an ECC91. It drew about 100 mA for a few seconds with no
    damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    The 100 mA is a current limit due to the limited electron emission
    possible from that cathode at those settings. You can get flash-over with
    anode voltage at the grid of toobs.

    There was a 1k current-limiting resistor in the HT supply (it changed >colour). At least I had time to get to the 'off' switch before the
    valve could be seriously damaged. Luckily I was testing with reduced HT >(about 100v) so the current would have been limited to about 100mA by
    the resistor, even if the maximum emission had been greater


    I understand you love toobs, sure toobs were nice

    I enjoy designing with them, rather than just copying well-worn
    circuits. There are still niches to be explored.

    A few years ago I set myself the task of designing a low-noise audio
    preamp using a grounded-grid first stage - the result was far better
    than I had expected because it had repercussions on the second stage and
    the mixing stage which greatly improved the overload performance and the
    S/N ratio of the whole amplifier. If I had invented that in the 1950s,
    I would be a lot richer now.

    I sent copies of the 'before' and 'after' circuits to a friend who is a
    great believer in the mystical properties of valves, but is otherwise
    quite sensible. It took him two days to get his mind around how the
    circuit actually worked.


    [...]
    9) touch screen????

    I have never needed a touch screen. The only time I have used them is
    at supermarkets and that was for their convenience, not mine.


    10) X-Ray emission from the monitor HV stabilizer tubes..

    Grossly over-hyped.

    One dy in teh studis (seventoes) fiorebrigade came in and started measuring al color monitor for Xrays
    Not a probel.
    The reason turned out to be that a collage of mine
    had e face burn after working / repairing a color monitor
    with the metal sheet around the HV stage (that also incorporated a PD100) removed.
    So your milage may vary:
    http://www.kronjaeger.com/hv-old/xray/tech/PD500/index.html


    [...]
    I modified it to drive that real old magnetic deflection TV set with
    transistors HV tronsformer, the works. Was an interesting learning
    curve... Never longed back to toobs after that.

    My first experience with transistors was building a simple automatic
    parking light for a car from a circuit in a magazine. It used a >photoconductive cell to switch a chain of ever-larger transistors and
    supply a 12v bulb. The idiot who 'designed' it had added negative
    feedback instead of positive feedback, so the bulb never went right out
    and never came full on. The heatsink got hot and it ran down the car
    battery in daylight.

    It took a long time after that before I felt happy with transistors.

    My first transistor was the OC13...
    used it in my self designed AM radio.
    https://www.radiomuseum.org/tubes/tube_oc13.html
    That first one lasted a few hours, testing at higher current etc was too much. You have to learn...
    Then got some higher frequency ones and build a one tranistor FM transmitter, dynamic mike in series with the supply to feed an oscillator,
    the small voltage variations from that mike were enough to change the Cce to change frequency
    thing was so sensitive you could hear a clock ticking in the room over the radio.
    And then there was OC16... then 2N3055, build several amplifiers with that... then BU208 for TV horizontal output stages.
    https://www.donberg.co.uk/catalogue/bu_208.html
    started using power MOSFETS like the IRL34N..


    In the early sixties we had a school band, guitarist wanted an amp
    so I went looking around in surplus shop,
    got a balanced transformer and 2 EL84 and some ECC triodes to drive it.
    Had no ideas of the math, just trying...
    the guitarist tried it, looked shocked,
    then said 'I like this sound'
    Tube sound like old Marshall amps
    https://nl.wikipedia.org/wiki/Marshall_Amplification
    Must have done something right, years later he called me for more stuff...

    For my exams in electronics school later I designed and build a 250 W PEP linear with a PE1/100
    https://www.rigpix.com/tubes/pe1100.htm
    did the SSB exiter too, all tubes.
    Antenna just a wire in the garden 7 MHz HAM band IIRc
    It would light a neon if you walked past it..

    In the early eighties bought a Sinclair ZX80 and got into programming
    quickly added stuff...
    wrote my own CP/M clone OS...
    https://panteltje.nl/panteltje/z80/index.html
    at work I used the first IBM PCs.. at home my Z80 system, that was faster, I had a real RAM disk.
    https://panteltje.nl/panteltje/z80/system14/diagrams/index.html

    It is all not that hard:
    https://panteltje.nl/panteltje/raspberry_pi_dvb-s_transmitter/
    https://panteltje.nl/panteltje/newsflex/download.html

    Microchip PICs can do a lot:
    https://panteltje.nl/panteltje/pic/index.html

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to Liz Tuddenham on Mon Dec 9 07:54:56 2024
    On Mon, 9 Dec 2024 09:33:35 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 21:08:42 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from
    transistors and ICs, you have to think a different way; they aren't
    just poor transistors, they have a different lifestyle altogether. >> >> >> >> >They also have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of
    the bit being heated by the overload. Some time later the energy
    reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the >> >> >> >triodes in an ECC91. It drew about 100 mA for a few seconds with no >> >> >> >damage. That's equivalent to mixing up the Base and Collector
    connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink
    available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks) >> >> >> and 30 kilowatts for 25 uSec.

    Into the gate?

    Don't do that.

    ...but that is the comparison with what I did by accident. I did it to
    a device that was designed as an RF amplifier with a rated dissipation
    of less than 3 watts and you were comparing it with a semiconductor that
    was massively bigger - and now you say don't do that - and the device
    needs extra protection components.

    That was the point I was making: you can get away with mishaps in a
    valve circuit that you can't get away with in a comparable transistor
    circuit.

    My first job interview, I told the guy that I preferred tubes to
    transistors because it was harder to blow up tubes. He sniffed and
    said "That won't do" and dismissed me.

    I was asked the same question at my first job interview. I just said I >understood valves better, which was true at the time. The Chief
    Engineer, who was interviewing me, then produced the circuit diagram of
    one of the firm's valve communications receivers and asked me to go
    through it and tell him what each part did.

    I took one look at it and said "Yuck! It's chassis-live". My
    interviewer let me continue and then gave me the job. It turned out
    later that he hated having to make the set that way but for commercial >reasons it had to work on 110v D.C. and therefore had to have the
    chassis connected to one pole of the mains. (The chassis was well
    insulated from the casing and all the outside fittings and connections.)

    Throughout the entire job with that firm, I never had to design with
    valves - but I did ten years later when I had to make some high voltage >research equipment.

    My Hallicrafters S38 was a metal box with a hot chassis inside and all
    the grommets had long ago failed. so I had to plug it in the right
    way, with unpolarized outlets. I attached a neon lamp to the top; if I
    touched it and it lit up, I'd switch the plug.

    People used to soak in their bathtub with a radio on the table. If it
    fell into the water, they would die.

    Life was cheap, back then.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From ehsjr@21:1/5 to john larkin on Mon Dec 9 15:23:00 2024
    On 12/8/2024 9:04 PM, john larkin wrote:
    On Wed, 4 Dec 2024 22:32:33 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Cooker hob ring?


    What's that in American ??!!

    :-)

    https://www.amazon.com/LXun-Electric-Included-Replacement-Whirlpool/dp/B08BLJYTD4/ref=asc_df_B08BLJYTD4?mcid=6a1fcb0f8a9b374fb92357f05f23bb39&hvocijid=12073860510026011302-B08BLJYTD4-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=692875362841&hvpos=&
    hvnetw=g&hvrand=12073860510026011302&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9004204&hvtargid=pla-2281435183338&psc=1

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From ehsjr@21:1/5 to john larkin on Mon Dec 9 15:38:13 2024
    On 12/9/2024 10:54 AM, john larkin wrote:
    On Mon, 9 Dec 2024 09:33:35 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 21:08:42 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 17:34:56 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <JL@gct.com> wrote:

    On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:

    Jan Panteltje <alien@comet.invalid> wrote:

    On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
    liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
    <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:

    john larkin <JL@gct.com> wrote:

    [...]>RL

    Tubes were awful. Still are.

    The techniques for designing with them are quite different from >>>>>>>>>> transistors and ICs, you have to think a different way; they aren't >>>>>>>>>> just poor transistors, they have a different lifestyle altogether. >>>>>>>>>> They also have some advantages over semiconductors:

    1) Withstanding short term overloads without damage.

    Thermal overloads depend on teh heatsink.

    Only slow overloads. Fast ones depend on the thermal time constant of >>>>>>>> the bit being heated by the overload. Some time later the energy >>>>>>>> reaches the heat sink but but then the damage is done.

    I've just accidentally mixed up the anode and grid pins of one of the >>>>>>>> triodes in an ECC91. It drew about 100 mA for a few seconds with no >>>>>>>> damage. That's equivalent to mixing up the Base and Collector >>>>>>>> connections on a transistor and subjecting the Base-Emitter junction to
    about 10 times the rated maximum Collector current. How many
    transistors would survive that, even with the biggest heatsink >>>>>>>> available?

    Mosfet data sheets usually have SOAR curves.

    IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks) >>>>>>> and 30 kilowatts for 25 uSec.

    Into the gate?

    Don't do that.

    ...but that is the comparison with what I did by accident. I did it to >>>> a device that was designed as an RF amplifier with a rated dissipation >>>> of less than 3 watts and you were comparing it with a semiconductor that >>>> was massively bigger - and now you say don't do that - and the device
    needs extra protection components.

    That was the point I was making: you can get away with mishaps in a
    valve circuit that you can't get away with in a comparable transistor
    circuit.

    My first job interview, I told the guy that I preferred tubes to
    transistors because it was harder to blow up tubes. He sniffed and
    said "That won't do" and dismissed me.

    I was asked the same question at my first job interview. I just said I
    understood valves better, which was true at the time. The Chief
    Engineer, who was interviewing me, then produced the circuit diagram of
    one of the firm's valve communications receivers and asked me to go
    through it and tell him what each part did.

    I took one look at it and said "Yuck! It's chassis-live". My
    interviewer let me continue and then gave me the job. It turned out
    later that he hated having to make the set that way but for commercial
    reasons it had to work on 110v D.C. and therefore had to have the
    chassis connected to one pole of the mains. (The chassis was well
    insulated from the casing and all the outside fittings and connections.)

    Throughout the entire job with that firm, I never had to design with
    valves - but I did ten years later when I had to make some high voltage
    research equipment.

    My Hallicrafters S38 was a metal box with a hot chassis inside and all
    the grommets had long ago failed. so I had to plug it in the right
    way, with unpolarized outlets. I attached a neon lamp to the top; if I touched it and it lit up, I'd switch the plug.

    My aunt had that radio & the same problem. I solved** it with a pair
    of dikes and gorilla forearms.

    ** at least for use in that specific location.

    Ed


    People used to soak in their bathtub with a radio on the table. If it
    fell into the water, they would die.

    Life was cheap, back then.


    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Mon Dec 9 14:37:00 2024
    On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
    wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
    temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Here's what I think we will do.

    https://www.dropbox.com/scl/fi/f8hijtr3vqfmz5kz0jupg/P970_Cooler_3D.jpg?rlkey=onklnfw11o4pdrs5ry5daqzwq&raw=1

    That's a Dynatron A41 cooler. I'm assuming we can dump 200 watts,
    pending testing in a real chassis.

    SolidWorks is great fun.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to ehsjr on Mon Dec 9 14:29:55 2024
    On Mon, 9 Dec 2024 15:23:00 -0500, ehsjr <ehsjr@verizon.net> wrote:

    On 12/8/2024 9:04 PM, john larkin wrote:
    On Wed, 4 Dec 2024 22:32:33 +0000, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    john larkin <jl@glen--canyon.com> wrote:

    I'm thinking about building a biggish rackmount dummy load box. It
    would simulate series resistance and inductance. Part of the problem
    is that it will need to dump a lot of heat.

    We are using copper CPU coolers on PC boards, which are great up to a
    couple of hundred watts, but I'd like to do a kilowatt or two.

    https://highlandtechnology.com/Product/P945

    It would take a heap of expensive extruded heat sinks and fans to get
    rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC >>>> temp rise.

    A small hair dryer can dump a kilowatt. So some sort of red-hot
    nichrome coils and a vicious fan might work.

    I'd prefer to not use water.

    I wonder if there is some sort of runs-red-hot power resistor.

    Cooker hob ring?


    What's that in American ??!!

    :-)

    https://www.amazon.com/LXun-Electric-Included-Replacement-Whirlpool/dp/B08BLJYTD4/ref=asc_df_B08BLJYTD4?mcid=6a1fcb0f8a9b374fb92357f05f23bb39&hvocijid=12073860510026011302-B08BLJYTD4-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=692875362841&hvpos=&
    hvnetw=g&hvrand=12073860510026011302&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9004204&hvtargid=pla-2281435183338&psc=1


    Oh, an electric stove heater element. At least one is usually broken.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)