As it's the only such prog. for decades, I don't want to criticise it
too much. This week's does feature some actual electronics - a valved wireless, and an '80s boombox (as well as a food mixer that has more electronics than I expected).
But basic TV presentation? This component has failed, here's the
replacement - out of focus? hardly any close-ups? A whole second to
look at them, if we're lucky? Also, the odd block diagramme wouldn't
go amiss - not enough to frighten the children/horses, but none at
all is too few. The voice commentary actually isn't bad at explaining
things (to a near-zero knowledge audience anyway), but would
certainly benefit from some visual aids. (It has good AD.)
One wonders who the prog. is actually aimed at. I'm sure a lot of it
is entertainment only - here are some funny men (they have all been
men so far, I think) who fix things as a sort of strange hobby;
however, it does give some information on how things work. But not at
people like us.
Once you've got into the habit of watching things like Mr Carlson's
Lab, Adamant IT, Northridge Fix and others like them, anything
supposedly informative about electronics on mainstream TV will be a
waste of your time. Youtube channels where the presenter shows us
their own material themselves are incomparably better because they
know what to show us because they understand it and have experience of
it and know what's important to point out. They may also have learnt
from mistakes and sometimes tell us about those so that we can learn
too. Their main objective is that we get to understand something of
the subject matter, whereas the main objective of TV producers is to concentrate on 'production values' rather than content and make
something attention grabbing and entertaining for other people like themselves who don't understand it at all.
As it's the only such prog. for decades, I don't want to criticise it
too much. This week's does feature some actual electronics - a valved >wireless, and an '80s boombox (as well as a food mixer that has more >electronics than I expected).
But basic TV presentation? This component has failed, here's the
replacement - out of focus? hardly any close-ups? A whole second to look
at them, if we're lucky? Also, the odd block diagramme wouldn't go amiss
- not enough to frighten the children/horses, but none at all is too
few. The voice commentary actually isn't bad at explaining things (to a >near-zero knowledge audience anyway), but would certainly benefit from
some visual aids. (It has good AD.)
One wonders who the prog. is actually aimed at. I'm sure a lot of it is >entertainment only - here are some funny men (they have all been men so
far, I think) who fix things as a sort of strange hobby; however, it
_does_ give some information on how things work. But not at people like
us.
On Tue, 15 Aug 2023 22:06:05 +0100, "J. P. Gilliver"[]
<G6JPG@255soft.uk> wrote:
But basic TV presentation? This component has failed, here's the >>replacement - out of focus? hardly any close-ups? A whole second to look
at them, if we're lucky? Also, the odd block diagramme wouldn't go amiss
- not enough to frighten the children/horses, but none at all is too
few. The voice commentary actually isn't bad at explaining things (to a >>near-zero knowledge audience anyway), but would certainly benefit from
some visual aids. (It has good AD.)
One wonders who the prog. is actually aimed at. I'm sure a lot of it is >>entertainment only - here are some funny men (they have all been men so >>far, I think) who fix things as a sort of strange hobby; however, it
_does_ give some information on how things work. But not at people like
us.
Once you've got into the habit of watching things like Mr Carlson's
Lab, Adamant IT, Northridge Fix and others like them, anything
supposedly informative about electronics on mainstream TV will be a
waste of your time. Youtube channels where the presenter shows us
their own material themselves are incomparably better because they
know what to show us because they understand it and have experience of
it and know what's important to point out. They may also have learnt
from mistakes and sometimes tell us about those so that we can learn
too. Their main objective is that we get to understand something of
the subject matter, whereas the main objective of TV producers is to >concentrate on 'production values' rather than content and make
something attention grabbing and entertaining for other people like >themselves who don't understand it at all.
Rod.--
As it's the only such prog. for decades, I don't want to criticise it too much. This week's does feature some actual electronics - a valved
wireless, and an '80s boombox (as well as a food mixer that has more electronics than I expected).
But basic TV presentation? This component has failed, here's the
replacement - out of focus? hardly any close-ups? A whole second to look
at them, if we're lucky? Also, the odd block diagramme wouldn't go amiss - not enough to frighten the children/horses, but none at all is too few.
The voice commentary actually isn't bad at explaining things (to a
near-zero knowledge audience anyway), but would certainly benefit from
some visual aids. (It has good AD.)
One wonders who the prog. is actually aimed at. I'm sure a lot of it is entertainment only - here are some funny men (they have all been men so
far, I think) who fix things as a sort of strange hobby; however, it
_does_ give some information on how things work. But not at people like
us.
--
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf
It's quickly getting to a place where privacy will be cause for suspicion.
- Mayayana in alt.windows7.general, 2018-11-6.
J. P. Gilliver wrote:
As it's the only such prog. for decades, I don't want to criticise it
too much. This week's does feature some actual electronics - a valved
wireless, and an '80s boombox (as well as a food mixer that has more
electronics than I expected).
But basic TV presentation? This component has failed, here's the
replacement - out of focus? hardly any close-ups? A whole second to
look at them, if we're lucky? Also, the odd block diagramme wouldn't
go amiss - not enough to frighten the children/horses, but none at
all is too few. The voice commentary actually isn't bad at explaining
things (to a near-zero knowledge audience anyway), but would
certainly benefit from some visual aids. (It has good AD.)
One wonders who the prog. is actually aimed at. I'm sure a lot of it
is entertainment only - here are some funny men (they have all been
men so far, I think) who fix things as a sort of strange hobby;
however, it does give some information on how things work. But not at
people like us.
I'm amazed at the prices. ?500 for an old boom box!!
--
On Tue, 15 Aug 2023 22:06:05 +0100, "J. P. Gilliver"
<G6JPG@255soft.uk> wrote:
As it's the only such prog. for decades, I don't want to criticise it
too much. This week's does feature some actual electronics - a valved >>wireless, and an '80s boombox (as well as a food mixer that has more >>electronics than I expected).
But basic TV presentation? This component has failed, here's the >>replacement - out of focus? hardly any close-ups? A whole second to look
at them, if we're lucky? Also, the odd block diagramme wouldn't go amiss
- not enough to frighten the children/horses, but none at all is too
few. The voice commentary actually isn't bad at explaining things (to a >>near-zero knowledge audience anyway), but would certainly benefit from
some visual aids. (It has good AD.)
One wonders who the prog. is actually aimed at. I'm sure a lot of it is >>entertainment only - here are some funny men (they have all been men so >>far, I think) who fix things as a sort of strange hobby; however, it
_does_ give some information on how things work. But not at people like
us.
Once you've got into the habit of watching things like Mr Carlson's
Lab, Adamant IT, Northridge Fix and others like them, anything
supposedly informative about electronics on mainstream TV will be a
waste of your time. Youtube channels where the presenter shows us
their own material themselves are incomparably better because they
know what to show us because they understand it and have experience of
it and know what's important to point out. They may also have learnt
from mistakes and sometimes tell us about those so that we can learn
too. Their main objective is that we get to understand something of
the subject matter, whereas the main objective of TV producers is to concentrate on 'production values' rather than content and make
something attention grabbing and entertaining for other people like themselves who don't understand it at all.
Rod.
On 16/08/2023 08:52, Roderick Stewart wrote:
You beat me to saying exactly the same
Once you've got into the habit of watching things like Mr Carlson's
Lab, Adamant IT, Northridge Fix and others like them, anything
supposedly informative about electronics on mainstream TV will be a
waste of your time. Youtube channels where the presenter shows us
their own material themselves are incomparably better because they
know what to show us because they understand it and have experience of
it and know what's important to point out. They may also have learnt
from mistakes and sometimes tell us about those so that we can learn
too. Their main objective is that we get to understand something of
the subject matter, whereas the main objective of TV producers is to
concentrate on 'production values' rather than content and make
something attention grabbing and entertaining for other people like
themselves who don't understand it at all.
Once you've got into the habit of watching things like Mr Carlson's
Lab, Adamant IT, Northridge Fix and others like them, anything
supposedly informative about electronics on mainstream TV will be a
waste of your time. Youtube channels where the presenter shows us
their own material themselves are incomparably better because they
know what to show us because they understand it and have experience of
it and know what's important to point out.
This guy does a deep dive into schematics at times, both TVs and computers,
"I replaced the main board of this TV with brand new parts made in 2023!" >https://www.youtube.com/watch?v=MoqflFfvkR0
Though I'd be a bit concerned about X-rays ...
On 16/08/2023 08:52, Roderick Stewart wrote:
Once you've got into the habit of watching things like Mr Carlson's
Lab, Adamant IT, Northridge Fix and others like them, anything
supposedly informative about electronics on mainstream TV will be a
waste of your time. Youtube channels where the presenter shows us
their own material themselves are incomparably better because they
know what to show us because they understand it and have experience of
it and know what's important to point out.
This guy does a deep dive into schematics at times, both TVs and computers,
"I replaced the main board of this TV with brand new parts made in 2023!" https://www.youtube.com/watch?v=MoqflFfvkR0
Though I'd be a bit concerned about X-rays ...
Yes so why don't they save their budget and pay for the youtube stuff and >shove it on mainstream telly?
On Wed, 16 Aug 2023 13:40:32 +0100, Adrian Caspersz
<email@here.invalid> wrote:
This guy does a deep dive into schematics at times, both TVs and computers, >>
"I replaced the main board of this TV with brand new parts made in 2023!" >>https://www.youtube.com/watch?v=MoqflFfvkR0
Though I'd be a bit concerned about X-rays ...
I thought most of the concern about x-rays in early colour TVs was
because they generated the EHT as a 25kV pulse which was then
rectified by a single thermionic valve. I may be wrong but my
understanding is that x-rays are generated when a high voltage stream
of electrons hits something in a vacuum. More recent TVs only
generated a pulse of about 8kV and didn't use valves at all, and no >semiconductor had the full 25kV across it, so does this still apply?
Rod.
On Wed, 16 Aug 2023 13:40:32 +0100, Adrian Caspersz
<email@here.invalid> wrote:
This guy does a deep dive into schematics at times, both TVs and computers, >>
"I replaced the main board of this TV with brand new parts made in 2023!" >>https://www.youtube.com/watch?v=MoqflFfvkR0
Though I'd be a bit concerned about X-rays ...
I thought most of the concern about x-rays in early colour TVs was
because they generated the EHT as a 25kV pulse which was then
rectified by a single thermionic valve. I may be wrong but my
understanding is that x-rays are generated when a high voltage stream
of electrons hits something in a vacuum. More recent TVs only
generated a pulse of about 8kV and didn't use valves at all, and no >semiconductor had the full 25kV across it, so does this still apply?
Rod.
On Wed, 16 Aug 2023 14:37:47 +0100, Roderick Stewart ><rjfs@escapetime.myzen.co.uk> wrote:
On Wed, 16 Aug 2023 13:40:32 +0100, Adrian Caspersz
<email@here.invalid> wrote:
This guy does a deep dive into schematics at times, both TVs and computers, >>>
"I replaced the main board of this TV with brand new parts made in 2023!" >>>https://www.youtube.com/watch?v=MoqflFfvkR0
Though I'd be a bit concerned about X-rays ...
I thought most of the concern about x-rays in early colour TVs was
because they generated the EHT as a 25kV pulse which was then
rectified by a single thermionic valve. I may be wrong but my
understanding is that x-rays are generated when a high voltage stream
of electrons hits something in a vacuum. More recent TVs only
generated a pulse of about 8kV and didn't use valves at all, and no >>semiconductor had the full 25kV across it, so does this still apply?
Rod.
Coincidence! I just sent some comments about colour TV. I was one of
the first engineers trained on colour TV, both NTSC and then PAL so I
was supposed to be an expert. I remember "rumours" about standing too
close to the early THORN sets. I would think that screening on the CRT
would stop any x-rays.
In the BBC workshops there were little glass tubes that we could fit
over the EHT rectifier valve if we had to spend any time round the
back of a display monitor. They were made of special glass intended to
reduce x-rays, and it was specifically the EHT rectifier that was said
to present the most danger. I suppose the x-rays would be generated by
the electrons hitting the anode of the rectifier. Those early monitors
used a 25kV pulse, unlike later ones that used smaller pulses and a
kind of zigzag arrangement of diodes and capacitors as a voltage
multiplier, usually a tripler. CRT displays are designed for people to
sit in front of them, so I don't think there can have been much x-ray >emission from the front.
Rod.
I don't think I've ever heard of the zigzag type of multiplier ever
being used with thermionic rectifiers (you'd need several such,
obviously), so I think they only became practical with solid-state >rectifiers.
On Wed, 16 Aug 2023 15:16:12 +0100, Stephen Wolstenholme ><stephenwolstenholme30@outlook.com> wrote:
On Wed, 16 Aug 2023 14:37:47 +0100, Roderick Stewart >><rjfs@escapetime.myzen.co.uk> wrote:
On Wed, 16 Aug 2023 13:40:32 +0100, Adrian Caspersz
<email@here.invalid> wrote:
This guy does a deep dive into schematics at times, both TVs and computers, >>>>
"I replaced the main board of this TV with brand new parts made in 2023!" >>>>https://www.youtube.com/watch?v=MoqflFfvkR0
Though I'd be a bit concerned about X-rays ...
I thought most of the concern about x-rays in early colour TVs was >>>because they generated the EHT as a 25kV pulse which was then
rectified by a single thermionic valve. I may be wrong but my >>>understanding is that x-rays are generated when a high voltage stream
of electrons hits something in a vacuum. More recent TVs only
generated a pulse of about 8kV and didn't use valves at all, and no >>>semiconductor had the full 25kV across it, so does this still apply?
Rod.
Coincidence! I just sent some comments about colour TV. I was one of
the first engineers trained on colour TV, both NTSC and then PAL so I
was supposed to be an expert. I remember "rumours" about standing too
close to the early THORN sets. I would think that screening on the CRT >>would stop any x-rays.
In the BBC workshops there were little glass tubes that we could fit
over the EHT rectifier valve if we had to spend any time round the
back of a display monitor. They were made of special glass intended to
reduce x-rays, and it was specifically the EHT rectifier that was said
to present the most danger. I suppose the x-rays would be generated by
the electrons hitting the anode of the rectifier. Those early monitors
used a 25kV pulse, unlike later ones that used smaller pulses and a
kind of zigzag arrangement of diodes and capacitors as a voltage
multiplier, usually a tripler. CRT displays are designed for people to
sit in front of them, so I don't think there can have been much x-ray >emission from the front.
Rod.
I once had to "maintain" an Italian gadget that projected film or
TV images onto a layer of oil and the reflection was displayed on a
cinema screen.
steve1001908@outlook.com wrote:
I once had to "maintain" an Italian gadget that projected film or
TV images onto a layer of oil and the reflection was displayed on a
cinema screen.
Probably the Swiss https://en.wikipedia.org/wiki/Eidophor
Only way to get bright cinema sized TV screens until LED walls, LCD and DLP projectors came along.
Angus Robertson wrote:
steve1001908@outlook.com wrote:
I once had to "maintain" an Italian gadget that projected film orProbably the Swiss https://en.wikipedia.org/wiki/Eidophor
TV images onto a layer of oil and the reflection was displayed on a
cinema screen.
Only way to get bright cinema sized TV screens until LED walls, LCD
and DLP
projectors came along.
Or a G.E Telaria
In message <kk6kkkFaskvU2@mid.individual.net> at Thu, 17 Aug 2023
14:11:50, Andy Burns <usenet@andyburns.uk> writes
Angus Robertson wrote:Weren't there some systems that used lasers, and either a mirror-drum or >coil-controlled mirrors? (Or was the Telaria such?)
steve1001908@outlook.com wrote:
I once had to "maintain" an Italian gadget that projected film orProbably the Swiss https://en.wikipedia.org/wiki/Eidophor
TV images onto a layer of oil and the reflection was displayed on a
cinema screen.
Only way to get bright cinema sized TV screens until LED walls, LCD
and DLP
projectors came along.
Or a G.E Telaria
The Swiss Eidophor system using a layer of oil was around but I
don't know how "similar" it was to the Italian system.
Andy Burns writes:
Angus Robertson wrote:
Probably the Swiss https://en.wikipedia.org/wiki/Eidophor
Or a G.E Telaria
Weren't there some systems that used lasers, and either a mirror-drum or coil-controlled mirrors?
(Or was the Telaria such?)
I don't think I've ever heard of the zigzag type of multiplier ever
being used with thermionic rectifiers (you'd need several such,
obviously), so I think they only became practical with solid-state rectifiers.
J. P. Gilliver wrote:[]
Andy Burns writes:
Angus Robertson wrote:
Probably the Swiss https://en.wikipedia.org/wiki/Eidophor
Or a G.E Telaria
Weren't there some systems that used lasers, and either a mirror-drum
or coil-controlled mirrors?
Probably came later, these two are 1940/50's and 1970/80's
(Or was the Telaria such?)
It also used an oil film, Mike Harrison got hold of one and tore it
down as he does with lots of other "electric stuff".
I once had to "maintain" an Italian gadget that projected film or
TV images onto a layer of oil and the reflection was displayed on a
cinema screen.
Probably the Swiss https://en.wikipedia.org/wiki/Eidophor
Only way to get bright cinema sized TV screens until LED walls, LCD and DLP projectors came along.
J. P. Gilliver wrote:
As it's the only such prog. for decades, I don't want to criticise it
too much. This week's does feature some actual electronics - a valved
wireless, and an '80s boombox (as well as a food mixer that has more
electronics than I expected).
But basic TV presentation? This component has failed, here's the
replacement - out of focus? hardly any close-ups? A whole second to
look at them, if we're lucky? Also, the odd block diagramme wouldn't
go amiss - not enough to frighten the children/horses, but none at
all is too few. The voice commentary actually isn't bad at explaining
things (to a near-zero knowledge audience anyway), but would
certainly benefit from some visual aids. (It has good AD.)
One wonders who the prog. is actually aimed at. I'm sure a lot of it
is entertainment only - here are some funny men (they have all been
men so far, I think) who fix things as a sort of strange hobby;
however, it does give some information on how things work. But not at
people like us.
I'm amazed at the prices. ?500 for an old boom box!!
I liked the way they summarised the functions of
capacitors in radios as coupling, decoupling, smoothing and tuning.
(Wow! coupling /and/ de-coupling!)
I'm not sure who this programme is intended for either. Just a
nostalgia trip I think. I liked the way they summarised the functions
of capacitors in radios as coupling, decoupling, smoothing and tuning.
(Wow! coupling /and/ de-coupling!)
Max Demian <max_demian@bigfoot.com> wrote:
[...]
I liked the way they summarised the functions of
capacitors in radios as coupling, decoupling, smoothing and tuning.
(Wow! coupling /and/ de-coupling!)
That's always been a difficult one to explain to beginners. If it goes
to earth, it can decouple two circuit that share the same power supply >because it couples the voltage variations to earth.
It is a bit like a nut and bolt, it can fix two items together so that >movement of one is transferred to tha other - or it can stop one of them >moving if the other one happens to be firmly fixed.
In message <1qfttdw.1v3yvhizoejzcN%liz@poppyrecords.invalid.invalid> at
Mon, 21 Aug 2023 18:49:07, Liz Tuddenham
<liz@poppyrecords.invalid.invalid> writes
Max Demian <max_demian@bigfoot.com> wrote:
[...]
I liked the way they summarised the functions of
capacitors in radios as coupling, decoupling, smoothing and tuning.
(Wow! coupling /and/ de-coupling!)
That's always been a difficult one to explain to beginners. If it goes
to earth, it can decouple two circuit that share the same power supply >because it couples the voltage variations to earth.
It is a bit like a nut and bolt, it can fix two items together so that >movement of one is transferred to tha other - or it can stop one of them >moving if the other one happens to be firmly fixed.
Good analogy.
Another concept is the relativity of signals. I can't remember where I
was confused and what enlightened me: I think it was that US circuits
(or "schematics") tended much more to _not_ draw a line along the bottom
of the signal flow path, instead just liberally sprinking earth or
ground symbols. I think it might have been a car wiring diag. that
caused me to see the light. (When car wiring tended to actually _use_
the chassis more.)
No that was right. Last week with the Spectrum, they did not mention quite why ram chips fail. It was because Uncle Clive bought duff chips with only half the chip working and then put links in the pcbs to use the good half. This tended to mean that the quality of the working bit could be said to be suspect. Certainly most of the ones I had had some stock faults. Ram was the main one, Then I think it was TRY, which was a little psu to make the p-5v from the +5 coming out of the regulator, If this failed badly it could take a ram chip with it, and failed to power add ons like vtx 500 modems and the like. The ULA often was damaged if things were pulled off the port while it was powered up, along with tr4.
On the tech level of the show, yes I agree. They never said what he did to clean up the vintage radios volume control, as from experience there was no other course but to replace it, since the leaky capacitors around there would have put DC on it and that is a good way to wear it out.
I was surprised the double sided record deck was fine after a new stylus a clen up and new belts. Its been my experience with another one of those that the thing tends to have major issues with tracking a whole album due to crap engineering in the various components in pararell tracking arms or worn bearing in the pivoted arms. Brian
On 16/08/2023 11:32, Brian Gaff wrote:[]
Reminds me of two power supply decisions:main one, Then I think it was TRY, which was a little psu to make the p-5v >> from the +5 coming out of the regulator, If this failed badly it could take >> a ram chip with it, and failed to power add ons like vtx 500 modems and the []
On 16/08/2023 11:32, Brian Gaff wrote:[]
[]main one, Then I think it was TRY, which was a little psu to make the
p-5v
from the +5 coming out of the regulator, If this failed badly it
could take
a ram chip with it, and failed to power add ons like vtx 500 modems
and the
Reminds me of two power supply decisions:
1. The Oric (and I presume the Oric Atmos), mostly TTL logic so needed a
+5 supply: the power supply they provided used a -5 regulator. I don't
know why: I can only guess that the common 7905 regulator was cheaper
than the 7805. It was fine with the basic computer, but got interesting
when you added peripherals, such as the disc drive, which had a beefier supply, which also powered the computer. (Having said that, I don't
remember it ever actually going wrong.)
2. (Earlier - same company, Tangerine [the Oric said Tangerine on the
PCB].) When the Tangerine came out, the ASTEC modulator (most home
computers then used a domestic TV as monitor, and had to provide RF as
few TVs had baseband input) - little tin box, common on virtually all
home computers! - was initially only available with a 6V rail. Since the
rest of the computer ran on 5V, it would have been tedious to provide a separate supply just for that - so they designed in a little circuit,
using IIRR the dot clock of 6 MHz (I think the computer ran on 0.75 MHz)
and a teeny inductor: my first experience of a switch-mode supply (only
about 3 components). (FWIW, it seemed to work fine.) [ASTEC subsequently
made the boxes to run on 5V.]
That reminds me - I did hear that one of the other machines around then (Nascom was it?) was laid out with computer layout software - but that
knew nothing of RF, and they included the modulator in what they gave
it; of course, it never worked, and they had to bodge in an ASTEC tin
box anyway. Whether this is true or not I've no idea.
On Sun 03/09/2023 14:20, J. P. Gilliver wrote:[]
1. The Oric (and I presume the Oric Atmos), mostly TTL logic so-5V was probably to work RS232 with +5V from elsewhere.
needed a +5 supply: the power supply they provided used a -5
regulator. I don't know why: I can only guess that the common 7905 >>regulator was cheaper than the 7805. It was fine with the basic
computer, but got interesting when you added peripherals, such as the
disc drive, which had a beefier supply, which also powered the
computer. (Having said that, I don't remember it ever actually going wrong.) []
I don't think I've ever heard of the zigzag type of multiplier ever
being used with thermionic rectifiers (you'd need several such,
obviously), so I think they only became practical with solid-state rectifiers.
J. P. Gilliver <G6JPG@255soft.uk> wrote:
[...]
I don't think I've ever heard of the zigzag type of multiplier ever
being used with thermionic rectifiers (you'd need several such,
obviously), so I think they only became practical with solid-state
rectifiers.
https://worldradiohistory.com/Archive-Company-Publications/Philips-Techn >ical-Review/40s/Philips-Technical-Review-1949.pdf
Page 123:
"Heating the Filaments of Valves in a Cascade Generator by Means of High >Frequency Current" by Tj. Douma & H.P.J. Brekoo.
... The only case I've come across in a TV set
was a little (11"?) dual-standard portable, which had a little D (2V)
valve hidden inside the LOPT casing (DY91 rings a bell?); it had two
(IIRR) turns of thicker wire wound round the LOPT core to drive its
heater.
...This is
described in a series of articles beginning on p.69 of:
https://worldradiohistory.com/Archive-Company-Publications/Philips-Techn ical-Review/40s/Philips-Technical-Review-1948.pdf
J. P. Gilliver <G6JPG@255soft.uk> wrote:
... The only case I've come across in a TV set
was a little (11"?) dual-standard portable, which had a little D (2V)
valve hidden inside the LOPT casing (DY91 rings a bell?); it had two
(IIRR) turns of thicker wire wound round the LOPT core to drive its
heater.
They were usually EY51 (6.3v heater). They had no base, so the >heater/cathode wires were soldered to the terminals of the LOPT with big >rounded solder blobs to reduce corona discharge. Possibly a DY51, with
lower heater requirements, would have been used in a portable set.
EY51s were also used in the tripler of the Philips projection
television, immersed in oil and sealed in a metal can. This is
described in a series of articles beginning on p.69 of: >https://worldradiohistory.com/Archive-Company-Publications/Philips-Techn >ical-Review/40s/Philips-Technical-Review-1949.pdf
In message <1qgojd0.8wdt9v1qiaif4N%liz@poppyrecords.invalid.invalid> at
Thu, 7 Sep 2023 08:56:22, Liz Tuddenham
<liz@poppyrecords.invalid.invalid> writes
J. P. Gilliver <G6JPG@255soft.uk> wrote:Most ingenious! I think only for professional equipment, though. Clever
[...]
I don't think I've ever heard of the zigzag type of multiplier ever
being used with thermionic rectifiers (you'd need several such,
obviously), so I think they only became practical with solid-state
rectifiers.
https://worldradiohistory.com/Archive-Company-Publications/Philips-Techn >>ical-Review/40s/Philips-Technical-Review-1949.pdf
Page 123:
"Heating the Filaments of Valves in a Cascade Generator by Means of High >>Frequency Current" by Tj. Douma & H.P.J. Brekoo.
to pass the h. f. up the same lines as the (presumably mains) frequency
being used to generate the EHT.
Of course, in a TV set the signal being rectified is moderately h. f. >(compared to mains, anyway). The only case I've come across in a TV set
was a little (11"?) dual-standard portable, which had a little D (2V)
valve hidden inside the LOPT casing (DY91 rings a bell?); it had two
(IIRR) turns of thicker wire wound round the LOPT core to drive its
heater. (Very simple valve - about the shape and size of a gherkin; just
a single pin sticking out the top for the EHT, I can't remember what it
had at the base.) I replaced it with a solid-state stick - can't
remember why, I think it became intermittent. (The stick gave a brighter >slightly smaller picture - I presume higher voltage, so brighter and >deflected less.) I never worked on (the EHT part of, anyway) any bigger
set, so I don't know if any used multiple valve rectifiers in a
multiplier arrangement; I'd have thought that would be a complex and >error-prone thing to design and keep going in a domestic setting
(compared to doing it with solid-state stick rectifiers when those
became available), but I could be wrong.
In article <FgN+IjZpKZ+kFwIR@255soft.uk>, J. P. Gilliver
<G6JPG@255soft.uk> scribeth thus
In message <1qgojd0.8wdt9v1qiaif4N%liz@poppyrecords.invalid.invalid> at >Thu, 7 Sep 2023 08:56:22, Liz Tuddenham
<liz@poppyrecords.invalid.invalid> writes
J. P. Gilliver <G6JPG@255soft.uk> wrote:Most ingenious! I think only for professional equipment, though. Clever
[...]
I don't think I've ever heard of the zigzag type of multiplier ever
being used with thermionic rectifiers (you'd need several such,
obviously), so I think they only became practical with solid-state
rectifiers.
https://worldradiohistory.com/Archive-Company-Publications/Philips-Techn >>ical-Review/40s/Philips-Technical-Review-1949.pdf
Page 123:
"Heating the Filaments of Valves in a Cascade Generator by Means of High >>Frequency Current" by Tj. Douma & H.P.J. Brekoo.
to pass the h. f. up the same lines as the (presumably mains) frequency >being used to generate the EHT.
Of course, in a TV set the signal being rectified is moderately h. f. >(compared to mains, anyway). The only case I've come across in a TV set
was a little (11"?) dual-standard portable, which had a little D (2V)
valve hidden inside the LOPT casing (DY91 rings a bell?); it had two
(IIRR) turns of thicker wire wound round the LOPT core to drive its
heater. (Very simple valve - about the shape and size of a gherkin; just
a single pin sticking out the top for the EHT, I can't remember what it
had at the base.) I replaced it with a solid-state stick - can't
remember why, I think it became intermittent. (The stick gave a brighter >slightly smaller picture - I presume higher voltage, so brighter and >deflected less.) I never worked on (the EHT part of, anyway) any bigger >set, so I don't know if any used multiple valve rectifiers in a
multiplier arrangement; I'd have thought that would be a complex and >error-prone thing to design and keep going in a domestic setting
(compared to doing it with solid-state stick rectifiers when those
became available), but I could be wrong.
Useful source the Valve museum. They have got the EY and DY wire ended
valves in there and I do remember Selenium rectifiers both mains voltage
and EHT could tell when they failed they simply stunk the house out!..
Useful source the Valve museum. They have got the EY and DY wire ended
valves in there and I do remember Selenium rectifiers both mains voltage
and EHT could tell when they failed they simply stunk the house out!..
Http://www.r-type.org/exhib/aaa1233.htm
tony sayer <tony@bancom.co.uk> wrote:
In article <FgN+IjZpKZ+kFwIR@255soft.uk>, J. P. Gilliver
<G6JPG@255soft.uk> scribeth thus
In message <1qgojd0.8wdt9v1qiaif4N%liz@poppyrecords.invalid.invalid> at
Thu, 7 Sep 2023 08:56:22, Liz Tuddenham
<liz@poppyrecords.invalid.invalid> writes
J. P. Gilliver <G6JPG@255soft.uk> wrote:Most ingenious! I think only for professional equipment, though. Clever
[...]
I don't think I've ever heard of the zigzag type of multiplier ever
being used with thermionic rectifiers (you'd need several such,
obviously), so I think they only became practical with solid-state
rectifiers.
https://worldradiohistory.com/Archive-Company-Publications/Philips-Techn >> >>ical-Review/40s/Philips-Technical-Review-1949.pdf
Page 123:
"Heating the Filaments of Valves in a Cascade Generator by Means of High >> >>Frequency Current" by Tj. Douma & H.P.J. Brekoo.
to pass the h. f. up the same lines as the (presumably mains) frequency
being used to generate the EHT.
Of course, in a TV set the signal being rectified is moderately h. f.
(compared to mains, anyway). The only case I've come across in a TV set
was a little (11"?) dual-standard portable, which had a little D (2V)
valve hidden inside the LOPT casing (DY91 rings a bell?); it had two
(IIRR) turns of thicker wire wound round the LOPT core to drive its
heater. (Very simple valve - about the shape and size of a gherkin; just
a single pin sticking out the top for the EHT, I can't remember what it
had at the base.) I replaced it with a solid-state stick - can't
remember why, I think it became intermittent. (The stick gave a brighter
slightly smaller picture - I presume higher voltage, so brighter and
deflected less.) I never worked on (the EHT part of, anyway) any bigger
set, so I don't know if any used multiple valve rectifiers in a
multiplier arrangement; I'd have thought that would be a complex and
error-prone thing to design and keep going in a domestic setting
(compared to doing it with solid-state stick rectifiers when those
became available), but I could be wrong.
Useful source the Valve museum. They have got the EY and DY wire ended
valves in there and I do remember Selenium rectifiers both mains voltage
and EHT could tell when they failed they simply stunk the house out!..
There was a story circulating in the late 1960s of a service engineer
who turned up to repair a television set. As the housewife opened the
door he took one sniff, walked back to the van and returned with a
selenium rectifier. He had diagnosed the problem without even entering
the house.
If you want to be reminded of the smell, try sniffing an anti-dandruff >shampoo which contains selenium sulphide.
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