From what cable is it coming? That would give you an idea of the working voltage. There is absolutely nothing readable in there any more?

ATX or AT power supply?

Wow nice old AT supply ! That cap should be on the secondary due to the proximity to the output inductors. If it is (try to follow traces on the bottom of board) then it would be most likely a 25v cap (being of the early 80's era) but the Farad value would be a guess at something around 1000uF. Check the small blue ones, they are also for the outputs so their voltage and value could halp give a hint as to that one.. (being 2-3 times the size ~ 2 -3 the uFd but same or higher voltage rating)

edit: there was someone else here working on an old very similar PSU a month or so ago, will try to search it out as there may be enough similarities to help figure out that cap.

It is an AT PSU. What do you mean "from what cable is it coming"?
Sadly there is absolutely nothing left from any writing on the cap.
This is the back side of the board. I marked the cap location. What should I trace?

Ok so it is the cap from before the actual output voltages, no cable to trace to. If the trace had been connected to for instance the 12V output I would advise a 16V capacitor, ofr 5V a 6.3V and so on. But since this one is before, 25V seems a good guess but as posted by Horun, maybe the other old PSU can give better clues as what voltage and capacitance to use. Thinking of it, if I am brave enough to dig into my little storage area, there's a XT clone in there from this era that might have information too that way.

You could email the people at https://www.schrack.com/ with that G070352 marking from the board and see if they still have the schematics somewhere, who knows.

Googleing around, I found a picture of a PSU that look exaclty like mine:
https://ibm-pc.webnode.sk/power-supplies/
IBM PC/XT 130W Power Supply #1
Placed in IBM PC 5150 rev. B
IBM Part Number: 1501438
Manufactured date: 21/86

some more googleing got me to this closeup pic:
https://www.nightfallcrew.com/gallery/persona … 51/IMG_7594.jpg
Still no good look on the side of the cap though.

Soo... does this mean it is a 16v 3300uf cap?

Yes, it does. Make sure you get a low-ESR variant. The good thing from that picture is it is also showing the polarity.

anetanel wrote on 2020-05-02, 14:17:

Soo... does this mean it is a 16v 3300uf cap?

Great detective work ! Yes that looks identical to this:
https://www.ebay.com/itm/2pcs-ROE-EKM-3300uF- … S-/223484824925
You can use any high quality 3300uf 16v 105c capacitor.

Hi, just a quick question on voltages you get on molex connector for this PSU. I have a similar one Schrack Eletronics EG 071068-D P/N 1501438. When powered without anything connected, on molex connector I get the 5V (between groud black wire and red wire - as expected), and nothing for the expected 12V (between ground and green wire).

Wondering if this is expected behaviour... no experience with these power sources - tying to troubleshoot an IBM 5160 😀

NOTE:
- I am getting different readings after multiple restarts of the PSU without drives connected and without motherboard connected: 0L instead 12V most of the times, and seldom 11.25V
- when I manage to get 11.25V a few times in a row, I connect either 10MB HDD or 356k floppy drive, and I can read 11.91V instead 11.25V when there is nothing connected

also, my PSU has the blue capacitor 16v 3300uf like this one here https://ibm-pc.webnode.sk/power-supplies/#&gid=1&pid=1