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Schematics or help with Compaq Deskpro 286 Power Supply - Tantalum Capacitor Values

booboo

booboo

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Sep 13, 2009
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Dallas, Texas, USA
Hello! I'm hoping someone has restored or has access to schematics to a Compaq Deskpro 286 power supply. It has 2 blown tantalum capacitors: C22 and C24. The picture shows the relative location of those. Unfortunately I didn't record the values before they blew :(

20220804_203536.jpg
 
Correct, one blown tantalum (C24) is behind the very large electrolytic... not possible to photograph. All the tantalums are like those little orange teardrops to the right. Some of those tantalum capacitors that remain are 15uF, 68uF. Some are 15V others 25V. There are more hidden behind the heatsinks and not visible. I have the technical reference and maintenance manuals, and while they do provide schematics for the motherboard and various cards, they omit the power supply.
 
That's not uncommon for many vendors--the PSU sometimes is sourced from various 3rd parties and, in any case, repair folks are strongly discouraged from repairing PSUs because of potential shock or fire liability.
However, given that both caps appear to be on the output side of the supply, I'd be tempted to strike a happy medium and replace both with 47µF 25V tants. At worst, you'll end up blowing one again. Be sure to observe polarity.
 
Thanks Chuck(G), that's helpful. I'm going to take a full inventory of the remaining tantalums. There's about 8 of them and ensure I correctly identified them. C22 remains seem to have some markings left. C24 is completely gone unfortunately.
 
I think I've got a deskpro 286 that I haven't smoked yet. After work today, I'll try to remember to open up the PSU and see if I can read the values, just to confirm.

I've got a deskpro 8086, which I think uses the same PSU, and when I turned it on it definitely released some smoke from the PSU area, but I'm not sure if it was the power supply or something on the motherboard nearby the power supply.
 
Thank you Jafir!!! Appreciate the effort... I've got a spare Deskpro 8086 power supply and have not turned on :) However opening up it's (a) significantly different design and (b) lower output spec'ed. I've found pictures of the Deskpro 386 power supply and that one is different as well.
 
Is your 286 an 8mhz or 12mhz? What are the specs of the PSU, just to make sure I'm looking at the correct stuff.
 
It's a 12Mhz. The Compaq FRU sticker states 48044, but the real part number for the power supply should be 108065-001 (12-Mhz PS). That is the one I'm seeking info on...

I mentioned that I have a spare PS which is 102927-001 (8-Mhz or 8086); that one will sit unpowered until I document the capacitors (in case it too blows up). But I don't want to use it due to lower output.
 
Well, I think it's solved. I've unsoldered the remains and was surprised there was indeed enough to determine the values with some certainty. Since there are other 15uF 25V capacitors, the markings seem in line. See the picture below, for sure they are 15uF, and the 5 on the one of the left seems to indicate 25V as others on the PS. The one on the right... well I'll just try 25V as well.although might be 16V due to narrower legs?:
20220805_111452.jpg
 
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