• Re: Component idenification

    From legg@21:1/5 to All on Sun Nov 6 16:05:00 2022
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all
    except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power
    dissipation, when in use and is expected to run warm.

    What is the actual current draw? Is your bulb dim?

    You should be able to identify parts from board designators
    and the reference manual.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to All on Sun Nov 6 20:48:15 2022
    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all
    except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to legg on Sun Nov 6 21:29:37 2022
    On Sun, 06 Nov 2022 16:05:00 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all >>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power
    dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Allison@21:1/5 to Cursitor Doom on Sun Nov 6 14:58:18 2022
    Cursitor Doom wrote:
    ________________________


    That's an NTC inrush limiter. It has roughly constant power
    dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA

    ** What about " RT1010" ???

    Resistor Thermal 7.5 ohms.



    ..... Phil

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Sun Nov 6 19:52:50 2022
    On Sun, 06 Nov 2022 21:29:37 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    On Sun, 06 Nov 2022 16:05:00 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com> >>wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all >>>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power
    dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    Then it's time to find the short cct.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to legg on Mon Nov 7 19:00:45 2022
    On Sun, 06 Nov 2022 19:52:50 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 21:29:37 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    On Sun, 06 Nov 2022 16:05:00 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com> >>>wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all >>>>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power
    dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    Then it's time to find the short cct.

    RL

    Sure is. I came across a section of the service manual I hadn't found
    before (I find service manuals in PDF format *so* difficult to
    navigate) and it's provided a list of parts to check in the event of
    this fault arising. The list is quite lenghty, but is at least limited
    by virtue of there being a multi-pronged jumper which interconnects
    certain sections and by removing that you can drastically reduce the
    number of parts to take a closer look at if the fault then clears,
    which it has. Fingers crossed, eh?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Peter W.@21:1/5 to All on Mon Nov 7 11:54:45 2022
    The list is quite lenghty, but is at least limited
    by virtue of there being a multi-pronged jumper which interconnects
    certain sections and by removing that you can drastically reduce the
    number of parts to take a closer look at if the fault then clears,
    which it has. Fingers crossed, eh?

    OK - if the fault clears when a jumper is removed, then you know that the fault is in the removed section, correct? Not the other way around?

    Too many individuals think it works the other way, sadly.

    Peter Wieck
    Melrose Park, PA

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to peterwieck33@gmail.com on Mon Nov 7 23:20:18 2022
    On Mon, 7 Nov 2022 11:54:45 -0800 (PST), "Peter W."
    <peterwieck33@gmail.com> wrote:

    The list is quite lenghty, but is at least limited
    by virtue of there being a multi-pronged jumper which interconnects
    certain sections and by removing that you can drastically reduce the
    number of parts to take a closer look at if the fault then clears,
    which it has. Fingers crossed, eh?

    OK - if the fault clears when a jumper is removed, then you know that the fault is in the removed section, correct? Not the other way around?

    Too many individuals think it works the other way, sadly.

    Yes, you're effectively removing the connection to the damaged
    section; the section which has some component in it which has gone low-resistance.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to legg on Mon Nov 7 23:22:26 2022
    On Sun, 06 Nov 2022 19:52:50 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 21:29:37 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    On Sun, 06 Nov 2022 16:05:00 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com> >>>wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all >>>>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power
    dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    Then it's time to find the short cct.

    RL

    This kind of fault would be so much easier to detect if we had IR
    glasses to view the suspect areas with. Someone really needs to invent
    those.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Peter W.@21:1/5 to All on Tue Nov 8 03:47:08 2022
    This kind of fault would be so much easier to detect if we had IR
    glasses to view the suspect areas with. Someone really needs to invent those.

    https://www.grainger.com/search/test-instruments/temperature-and-environmental-measurement/infrared-temperature-measurement/infrared-cameras?filters=webParentSkuKey&webParentSkuKey=WP8398465 Not cheap. The lenses exist - military versions for the most
    part. But not particularly fine-pitched.

    Peter Wieck
    Melrose Park, PA

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Tue Nov 8 12:10:25 2022
    On Mon, 07 Nov 2022 23:22:26 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    On Sun, 06 Nov 2022 19:52:50 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 21:29:37 +0000, Cursitor Doom <cd@notformail.com> >>wrote:

    On Sun, 06 Nov 2022 16:05:00 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com> >>>>wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes >>>>>and fired up the faulty 'scope, this component gets hot. I'm not >>>>>really sure what it is, though and there are no markings on it at all >>>>>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power >>>>dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    Then it's time to find the short cct.

    RL

    This kind of fault would be so much easier to detect if we had IR
    glasses to view the suspect areas with. Someone really needs to invent
    those.

    You should be able to track a short this close to the
    AC input with a multimeter on diode test mode.

    brodge rec,
    inverter fets
    bulk caps

    to start.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From three_jeeps@21:1/5 to legg on Tue Nov 8 10:36:41 2022
    On Tuesday, November 8, 2022 at 12:09:23 PM UTC-5, legg wrote:
    On Mon, 07 Nov 2022 23:22:26 +0000, Cursitor Doom <c...@notformail.com> wrote:

    On Sun, 06 Nov 2022 19:52:50 -0500, legg <le...@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 21:29:37 +0000, Cursitor Doom <c...@notformail.com> >>wrote:

    On Sun, 06 Nov 2022 16:05:00 -0500, legg <le...@nospam.magma.ca> wrote: >>>
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <c...@notformail.com> >>>>wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes >>>>>and fired up the faulty 'scope, this component gets hot. I'm not >>>>>really sure what it is, though and there are no markings on it at all >>>>>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power >>>>dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on >>>the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    Then it's time to find the short cct.

    RL

    This kind of fault would be so much easier to detect if we had IR
    glasses to view the suspect areas with. Someone really needs to invent >those.
    You should be able to track a short this close to the
    AC input with a multimeter on diode test mode.

    brodge rec,
    inverter fets
    bulk caps

    to start.

    RL

    yes, and actually, tracking down the short on the downstream sections (modules) should not be that difficult either, using the same approach. After all the faulty component is SHORTED which should be easy to find. Yea, it is a PITA to check every single
    component (sort of the brute force way to check), but judicious studying of the schematic and identifying appropriate points to isolate and subsequently test can prune away a number of branches in the tree fairly quickly so as to speak.

    Maybe bounce over to the tek google groups and ask if there are any common component failures that should be targeted first?
    Otherwise, enjoy getting intimate with the guts of your scope....

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to legg on Wed Nov 9 12:27:27 2022
    On Tue, 08 Nov 2022 12:10:25 -0500, legg <legg@nospam.magma.ca> wrote:

    On Mon, 07 Nov 2022 23:22:26 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    On Sun, 06 Nov 2022 19:52:50 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 21:29:37 +0000, Cursitor Doom <cd@notformail.com> >>>wrote:

    On Sun, 06 Nov 2022 16:05:00 -0500, legg <legg@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com> >>>>>wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes >>>>>>and fired up the faulty 'scope, this component gets hot. I'm not >>>>>>really sure what it is, though and there are no markings on it at all >>>>>>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power >>>>>dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    Then it's time to find the short cct.

    RL

    This kind of fault would be so much easier to detect if we had IR
    glasses to view the suspect areas with. Someone really needs to invent >>those.

    You should be able to track a short this close to the
    AC input with a multimeter on diode test mode.

    brodge rec,
    inverter fets
    bulk caps

    to start.

    RL

    Turns out those early items in the power chain are fine, so I'm moving
    on down the line to the less obvious items. The service manual has a
    list of chief suspects to look at first, so hopefully that should
    prove invaluable.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to jjhudak@gmail.com on Wed Nov 9 12:28:31 2022
    On Tue, 8 Nov 2022 10:36:41 -0800 (PST), three_jeeps
    <jjhudak@gmail.com> wrote:

    On Tuesday, November 8, 2022 at 12:09:23 PM UTC-5, legg wrote:
    On Mon, 07 Nov 2022 23:22:26 +0000, Cursitor Doom <c...@notformail.com>
    wrote:

    On Sun, 06 Nov 2022 19:52:50 -0500, legg <le...@nospam.magma.ca> wrote:

    On Sun, 06 Nov 2022 21:29:37 +0000, Cursitor Doom <c...@notformail.com>
    wrote:

    On Sun, 06 Nov 2022 16:05:00 -0500, legg <le...@nospam.magma.ca> wrote: >> >>>
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <c...@notformail.com> >> >>>>wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all >> >>>>>except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ

    That's an NTC inrush limiter. It has roughly constant power
    dissipation, when in use and is expected to run warm.

    That's what I thought too. But there's no such component visible on
    the schematic:


    https://disk.yandex.com/i/UhxATIy-6Y0LIA


    What is the actual current draw? Is your bulb dim?

    4x40W bulbs for 160W all together and they're all full-on.

    You should be able to identify parts from board designators
    and the reference manual.

    Then it's time to find the short cct.

    RL

    This kind of fault would be so much easier to detect if we had IR
    glasses to view the suspect areas with. Someone really needs to invent
    those.
    You should be able to track a short this close to the
    AC input with a multimeter on diode test mode.

    brodge rec,
    inverter fets
    bulk caps

    to start.

    RL

    yes, and actually, tracking down the short on the downstream sections (modules) should not be that difficult either, using the same approach. After all the faulty component is SHORTED which should be easy to find. Yea, it is a PITA to check every
    single component (sort of the brute force way to check), but judicious studying of the schematic and identifying appropriate points to isolate and subsequently test can prune away a number of branches in the tree fairly quickly so as to speak.

    Maybe bounce over to the tek google groups and ask if there are any common component failures that should be targeted first?
    Otherwise, enjoy getting intimate with the guts of your scope....

    Yup. Totally agree. I'm doing just that now.....

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to All on Thu Nov 10 17:57:11 2022
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all
    except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ


    Got 'er!

    I'm not at all familiar with the topology they've used in this PSU,
    but I believe it's the chopper transistor (I should have guessed)
    that's gone low-resistance: Q1050. It was releasing quite a bit of
    heat even at only 18VAC supply with the current limited via 4x40 bulbs
    to boot. I removed it from circuit to check and it was dead. So I'm
    hoping that's the only part that's been damaged. It's an IRF820 and I
    have a bunch of IRF840s so will press one of those into service in
    place of the burnt-out one. Pin-outs just the same, just a lower Rdson
    figure, which is no bad thing.
    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this? It doesn't seem like a very good way of ensuring
    thermal conductivity. :-/


    https://disk.yandex.com/i/cJDolujNfYucYw

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From whit3rd@21:1/5 to Cursitor Doom on Fri Nov 11 00:35:03 2022
    On Thursday, November 10, 2022 at 9:57:16 AM UTC-8, Cursitor Doom wrote:

    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this?

    That'd be 'silicone' grease; the picture showing studs over the power package indicates
    that an L-shaped or Z-shaped pressure arm (maybe three separate ones) was designed
    into the system. Why else would there be a threaded rod there?

    <https://e2e.ti.com/resized-image/__size/1230x0/__key/communityserver-discussions-components-files/196/7888.Mounting-a-TO220.png>

    <https://media.rs-online.com/t_large/RD504059-01.jpg>

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to All on Fri Nov 11 15:31:20 2022
    On Fri, 11 Nov 2022 00:35:03 -0800 (PST), whit3rd <whit3rd@gmail.com>
    wrote:

    On Thursday, November 10, 2022 at 9:57:16 AM UTC-8, Cursitor Doom wrote:

    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this?

    That'd be 'silicone' grease; the picture showing studs over the power package indicates
    that an L-shaped or Z-shaped pressure arm (maybe three separate ones) was designed
    into the system. Why else would there be a threaded rod there?

    <https://e2e.ti.com/resized-image/__size/1230x0/__key/communityserver-discussions-components-files/196/7888.Mounting-a-TO220.png>

    <https://media.rs-online.com/t_large/RD504059-01.jpg>


    If that's the case, maybe it was removed at some time, shortening the
    life of the chopper. I'll do something about that regardless. BTW, the
    threaded rods are there to retain plastic covers which encase the 3
    devices (don't ask me why as I haven't a clue what purpose they serve
    but certainly not to press bear the transistors to the heatsink, that
    much is certain).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From JC@21:1/5 to Cursitor Doom on Fri Nov 11 12:41:19 2022
    Cursitor Doom wrote:
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all
    except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ


    Got 'er!

    I'm not at all familiar with the topology they've used in this PSU,
    but I believe it's the chopper transistor (I should have guessed)
    that's gone low-resistance: Q1050. It was releasing quite a bit of
    heat even at only 18VAC supply with the current limited via 4x40 bulbs
    to boot. I removed it from circuit to check and it was dead. So I'm
    hoping that's the only part that's been damaged. It's an IRF820 and I
    have a bunch of IRF840s so will press one of those into service in
    place of the burnt-out one. Pin-outs just the same, just a lower Rdson figure, which is no bad thing.
    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this? It doesn't seem like a very good way of ensuring
    thermal conductivity. :-/


    https://disk.yandex.com/i/cJDolujNfYucYw

    look at the third photo, you will see that you have a lot of parts
    missing.

    https://bradthx.blogspot.com/2017/05/tektronix-2465b-capacitor-replacement.html

    you should also change out the 0.01uf cap, it has tendency to burn up
    that area.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From legg@21:1/5 to All on Fri Nov 11 13:34:01 2022
    On Fri, 11 Nov 2022 15:31:20 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    On Fri, 11 Nov 2022 00:35:03 -0800 (PST), whit3rd <whit3rd@gmail.com>
    wrote:

    On Thursday, November 10, 2022 at 9:57:16 AM UTC-8, Cursitor Doom wrote:

    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this?

    That'd be 'silicone' grease; the picture showing studs over the power package indicates
    that an L-shaped or Z-shaped pressure arm (maybe three separate ones) was designed
    into the system. Why else would there be a threaded rod there?
    <https://e2e.ti.com/resized-image/__size/1230x0/__key/communityserver-discussions-components-files/196/7888.Mounting-a-TO220.png>

    <https://media.rs-online.com/t_large/RD504059-01.jpg>


    If that's the case, maybe it was removed at some time, shortening the
    life of the chopper. I'll do something about that regardless. BTW, the >threaded rods are there to retain plastic covers which encase the 3
    devices (don't ask me why as I haven't a clue what purpose they serve
    but certainly not to press bear the transistors to the heatsink, that
    much is certain).

    The 'plastic' covers may serve the purpose of forced device retension.

    Depends on material composition and design.

    'just leaning' is not what is intended here.
    ...

    Diode test for other shorts.

    Check resistance gate to source pads of empty fet location.

    Should read diode drop minimum, or gate drive cct is
    compromised.

    RL

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From JC@21:1/5 to Cursitor Doom on Fri Nov 11 15:40:30 2022
    Cursitor Doom wrote:
    On Fri, 11 Nov 2022 12:41:19 -0500, JC <Chipbee40_SpamNo@yahoo.com>
    wrote:

    Cursitor Doom wrote:
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all
    except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ


    Got 'er!

    I'm not at all familiar with the topology they've used in this PSU,
    but I believe it's the chopper transistor (I should have guessed)
    that's gone low-resistance: Q1050. It was releasing quite a bit of
    heat even at only 18VAC supply with the current limited via 4x40 bulbs
    to boot. I removed it from circuit to check and it was dead. So I'm
    hoping that's the only part that's been damaged. It's an IRF820 and I
    have a bunch of IRF840s so will press one of those into service in
    place of the burnt-out one. Pin-outs just the same, just a lower Rdson
    figure, which is no bad thing.
    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this? It doesn't seem like a very good way of ensuring
    thermal conductivity. :-/


    https://disk.yandex.com/i/cJDolujNfYucYw

    look at the third photo, you will see that you have a lot of parts
    missing.

    https://bradthx.blogspot.com/2017/05/tektronix-2465b-capacitor-replacement.html

    Not sure what you mean by "a lot of parts missing" as I do have the individual plastic transistor covers shown in your photo but not in
    the one I posted of mine. Apart from those covers (which were out of
    shot in the picture I posted) there's nothing else missing AFAIK -
    apart from whatever fastening they used to hold the trannies against
    the heat sink (assuming they used something at all which they
    certainly *should* have, I'd have thought).

    you should also change out the 0.01uf cap, it has tendency to burn up
    that area.

    Yes, that and the two other RIFAs on that board. They all look end of
    life AFAICT.

    The plastic covers hold the transistors against the ceramic heatsink
    insulator. They are bolted on as shown in the photo.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to legg on Fri Nov 11 20:25:05 2022
    On Fri, 11 Nov 2022 13:34:01 -0500, legg <legg@nospam.magma.ca> wrote:

    On Fri, 11 Nov 2022 15:31:20 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    On Fri, 11 Nov 2022 00:35:03 -0800 (PST), whit3rd <whit3rd@gmail.com> >>wrote:

    On Thursday, November 10, 2022 at 9:57:16 AM UTC-8, Cursitor Doom wrote:

    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this?

    That'd be 'silicone' grease; the picture showing studs over the power package indicates
    that an L-shaped or Z-shaped pressure arm (maybe three separate ones) was designed
    into the system. Why else would there be a threaded rod there?
    <https://e2e.ti.com/resized-image/__size/1230x0/__key/communityserver-discussions-components-files/196/7888.Mounting-a-TO220.png>

    <https://media.rs-online.com/t_large/RD504059-01.jpg>


    If that's the case, maybe it was removed at some time, shortening the
    life of the chopper. I'll do something about that regardless. BTW, the >>threaded rods are there to retain plastic covers which encase the 3
    devices (don't ask me why as I haven't a clue what purpose they serve
    but certainly not to press bear the transistors to the heatsink, that
    much is certain).

    The 'plastic' covers may serve the purpose of forced device retension.

    Depends on material composition and design.

    'just leaning' is not what is intended here.
    ...

    Diode test for other shorts.

    Check resistance gate to source pads of empty fet location.

    Should read diode drop minimum, or gate drive cct is

    "cct"? Is that short for circuit?

    compromised.

    RL

    Thank you, Legg, I shall duly do so. I'm just hoping the transformer
    windings are still okay and that the shorted chopper hasn't sucked too
    much current through them, 'cos that would probably be terminal for
    the scope.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to All on Fri Nov 11 20:21:31 2022
    On Fri, 11 Nov 2022 12:41:19 -0500, JC <Chipbee40_SpamNo@yahoo.com>
    wrote:

    Cursitor Doom wrote:
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all
    except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ


    Got 'er!

    I'm not at all familiar with the topology they've used in this PSU,
    but I believe it's the chopper transistor (I should have guessed)
    that's gone low-resistance: Q1050. It was releasing quite a bit of
    heat even at only 18VAC supply with the current limited via 4x40 bulbs
    to boot. I removed it from circuit to check and it was dead. So I'm
    hoping that's the only part that's been damaged. It's an IRF820 and I
    have a bunch of IRF840s so will press one of those into service in
    place of the burnt-out one. Pin-outs just the same, just a lower Rdson
    figure, which is no bad thing.
    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this? It doesn't seem like a very good way of ensuring
    thermal conductivity. :-/


    https://disk.yandex.com/i/cJDolujNfYucYw

    look at the third photo, you will see that you have a lot of parts
    missing.

    https://bradthx.blogspot.com/2017/05/tektronix-2465b-capacitor-replacement.html

    Not sure what you mean by "a lot of parts missing" as I do have the
    individual plastic transistor covers shown in your photo but not in
    the one I posted of mine. Apart from those covers (which were out of
    shot in the picture I posted) there's nothing else missing AFAIK -
    apart from whatever fastening they used to hold the trannies against
    the heat sink (assuming they used something at all which they
    certainly *should* have, I'd have thought).

    you should also change out the 0.01uf cap, it has tendency to burn up
    that area.

    Yes, that and the two other RIFAs on that board. They all look end of
    life AFAICT.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to All on Fri Nov 11 23:08:12 2022
    On Fri, 11 Nov 2022 15:40:30 -0500, JC <Chipbee40_SpamNo@yahoo.com>
    wrote:

    Cursitor Doom wrote:
    On Fri, 11 Nov 2022 12:41:19 -0500, JC <Chipbee40_SpamNo@yahoo.com>
    wrote:

    Cursitor Doom wrote:
    On Sun, 06 Nov 2022 20:48:15 +0000, Cursitor Doom <cd@notformail.com>
    wrote:

    Gentlemen,

    Having put together a dim bulb tester for current-limiting purposes
    and fired up the faulty 'scope, this component gets hot. I'm not
    really sure what it is, though and there are no markings on it at all >>>>> except for two tiny blobs of paint.
    Anyone know?


    https://disk.yandex.com/i/jmR716xUNBt8OQ


    Got 'er!

    I'm not at all familiar with the topology they've used in this PSU,
    but I believe it's the chopper transistor (I should have guessed)
    that's gone low-resistance: Q1050. It was releasing quite a bit of
    heat even at only 18VAC supply with the current limited via 4x40 bulbs >>>> to boot. I removed it from circuit to check and it was dead. So I'm
    hoping that's the only part that's been damaged. It's an IRF820 and I
    have a bunch of IRF840s so will press one of those into service in
    place of the burnt-out one. Pin-outs just the same, just a lower Rdson >>>> figure, which is no bad thing.
    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this? It doesn't seem like a very good way of ensuring
    thermal conductivity. :-/


    https://disk.yandex.com/i/cJDolujNfYucYw

    look at the third photo, you will see that you have a lot of parts
    missing.

    https://bradthx.blogspot.com/2017/05/tektronix-2465b-capacitor-replacement.html

    Not sure what you mean by "a lot of parts missing" as I do have the
    individual plastic transistor covers shown in your photo but not in
    the one I posted of mine. Apart from those covers (which were out of
    shot in the picture I posted) there's nothing else missing AFAIK -
    apart from whatever fastening they used to hold the trannies against
    the heat sink (assuming they used something at all which they
    certainly *should* have, I'd have thought).

    you should also change out the 0.01uf cap, it has tendency to burn up
    that area.

    Yes, that and the two other RIFAs on that board. They all look end of
    life AFAICT.

    The plastic covers hold the transistors against the ceramic heatsink >insulator. They are bolted on as shown in the photo.

    You are correct. I've taken a closer look now and they do have that
    capability; many thanks.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Cursitor Doom@21:1/5 to robin_listas@es.invalid on Sun Nov 13 22:50:18 2022
    On Sun, 13 Nov 2022 23:17:29 +0100, "Carlos E.R."
    <robin_listas@es.invalid> wrote:

    On 2022-11-11 16:31, Cursitor Doom wrote:
    On Fri, 11 Nov 2022 00:35:03 -0800 (PST), whit3rd <whit3rd@gmail.com>
    wrote:

    On Thursday, November 10, 2022 at 9:57:16 AM UTC-8, Cursitor Doom wrote: >>>
    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this?

    That'd be 'silicone' grease; the picture showing studs over the power package indicates
    that an L-shaped or Z-shaped pressure arm (maybe three separate ones) was designed
    into the system. Why else would there be a threaded rod there?

    <https://e2e.ti.com/resized-image/__size/1230x0/__key/communityserver-discussions-components-files/196/7888.Mounting-a-TO220.png>

    <https://media.rs-online.com/t_large/RD504059-01.jpg>


    If that's the case, maybe it was removed at some time, shortening the
    life of the chopper. I'll do something about that regardless. BTW, the
    threaded rods are there to retain plastic covers which encase the 3
    devices (don't ask me why as I haven't a clue what purpose they serve
    but certainly not to press bear the transistors to the heatsink, that
    much is certain).

    I would guess insulation - is that part connected to mains?

    We eventually got to the bottom of it. The plastic covers are supposed
    to bear against the transistors underneath and hold them tight against
    the heatsink assembly. But it's a really unsatisfactory approach,
    because they're not secured at the bottom in any way, so the devices
    are not pressed evenly against their pads. I'm looking into whether it
    can be improved whilst waiting for the spares to arrive. Perhaps I can
    get some of those clips that Whit3rd posted a link to.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Carlos E.R.@21:1/5 to Cursitor Doom on Sun Nov 13 23:17:29 2022
    On 2022-11-11 16:31, Cursitor Doom wrote:
    On Fri, 11 Nov 2022 00:35:03 -0800 (PST), whit3rd <whit3rd@gmail.com>
    wrote:

    On Thursday, November 10, 2022 at 9:57:16 AM UTC-8, Cursitor Doom wrote:

    One question, though: they've mounted these transistors without using
    a screw through the mounting tab of this TO-220 package. The devices
    are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this?

    That'd be 'silicone' grease; the picture showing studs over the power package indicates
    that an L-shaped or Z-shaped pressure arm (maybe three separate ones) was designed
    into the system. Why else would there be a threaded rod there?

    <https://e2e.ti.com/resized-image/__size/1230x0/__key/communityserver-discussions-components-files/196/7888.Mounting-a-TO220.png>

    <https://media.rs-online.com/t_large/RD504059-01.jpg>


    If that's the case, maybe it was removed at some time, shortening the
    life of the chopper. I'll do something about that regardless. BTW, the threaded rods are there to retain plastic covers which encase the 3
    devices (don't ask me why as I haven't a clue what purpose they serve
    but certainly not to press bear the transistors to the heatsink, that
    much is certain).

    I would guess insulation - is that part connected to mains?


    --
    Cheers, Carlos.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Carlos E.R.@21:1/5 to Cursitor Doom on Wed Nov 16 20:40:39 2022
    On 2022-11-13 23:50, Cursitor Doom wrote:
    On Sun, 13 Nov 2022 23:17:29 +0100, "Carlos E.R."
    <robin_listas@es.invalid> wrote:

    On 2022-11-11 16:31, Cursitor Doom wrote:
    On Fri, 11 Nov 2022 00:35:03 -0800 (PST), whit3rd <whit3rd@gmail.com>
    wrote:

    On Thursday, November 10, 2022 at 9:57:16 AM UTC-8, Cursitor Doom wrote: >>>>
    One question, though: they've mounted these transistors without using >>>>> a screw through the mounting tab of this TO-220 package. The devices >>>>> are just 'leaning' against some white pad mounted on the heat sink
    (see photo). Is there some special grease required to mate the
    transistor to the white pad or can I just use the regular silicon
    grease for this?

    That'd be 'silicone' grease; the picture showing studs over the power package indicates
    that an L-shaped or Z-shaped pressure arm (maybe three separate ones) was designed
    into the system. Why else would there be a threaded rod there?

    <https://e2e.ti.com/resized-image/__size/1230x0/__key/communityserver-discussions-components-files/196/7888.Mounting-a-TO220.png>

    <https://media.rs-online.com/t_large/RD504059-01.jpg>


    If that's the case, maybe it was removed at some time, shortening the
    life of the chopper. I'll do something about that regardless. BTW, the
    threaded rods are there to retain plastic covers which encase the 3
    devices (don't ask me why as I haven't a clue what purpose they serve
    but certainly not to press bear the transistors to the heatsink, that
    much is certain).

    I would guess insulation - is that part connected to mains?

    We eventually got to the bottom of it. The plastic covers are supposed
    to bear against the transistors underneath and hold them tight against
    the heatsink assembly. But it's a really unsatisfactory approach,
    because they're not secured at the bottom in any way, so the devices
    are not pressed evenly against their pads. I'm looking into whether it
    can be improved whilst waiting for the spares to arrive. Perhaps I can
    get some of those clips that Whit3rd posted a link to.

    maybe drill a hole to put a small bolt?

    --
    Cheers, Carlos.

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