Whoo71 wrote on 2020-12-22, 05:11:

IMG_20201221_235420.jpg

That's a Delta, it means quality. Worth repairing imho.

• All resistors appear to be faulty, reading ohms well below what they're rated for
• Both diodes on the board appear to be shorted (~.6V in one direction, >2V in the other)

Have you testing in circuit or out of circuit? In circuit of course you are going to have stuff in parallel leading to lower resistance and other weird stuff.

transformers (which look like they may be the source of that residue all over the board?).

Isn't that just leftover flux with maybe a hint of cap juice?

Or would it be better to cut my losses and see if I can find a similarly sized AT power supply and stuff it in the enclosure here?

It would probably be the quickest way, yes, but keep in mind most older PSU (except name brand stuff, like Delta, Astec, LiteON, FSP...) were mostly garbage.
I'd say test the caps, especially the small ones that can prevent the psu from starting at all, and see how they are. Also,

IMG_20201221_212607.jpg

I can't tell, is it just a reflection or does that 6 pin DIP have a crack in it?

andrea wrote on 2020-12-22, 09:43:

Have you testing in circuit or out of circuit? In circuit of course you are going to have stuff in parallel leading to lower resistance and other weird stuff.

It was in circuit, so yes that would likely be why I was seeing those numbers.

andrea wrote on 2020-12-22, 09:43:

Isn't that just leftover flux with maybe a hint of cap juice?

Does flux tend to turn that dark brown color in systems this old?

I did also remove capacitors where there was a huge concentration of the stuff:

It was also up on the legs of some of the capacitors, so that would suggest that it's leaky capacitors that caused that residue. I'd think there would be way more corrosion though; the only corrosion I can see on the board is on the screws for the MOSFETs. Regardless, I think I'll re-cap the whole board and give it a good cleaning to get that stuff off.

andrea wrote on 2020-12-22, 09:43:

I can't tell, is it just a reflection or does that 6 pin DIP have a crack in it?

Looks like it's just the reflection.

Whoo71 wrote on 2020-12-24, 06:01:

I did also remove capacitors where there was a huge concentration of the stuff:

Ah no, that's just 100% capacitor. Clean the board, recap, and see what happens. Probably it'll start working.

Hi all,
I have just found this site and was surprised to find this post.
I have one of these pcs which I got around 1993-94. It was a great pc to use in it's day but I left it lying in a garage so it needs some TLC.
My problem is also with the power supply which is in bad shape. I noticed most of the semiconductors are corroded but they were easy enough to find online.
I think my main problem will be with the SMD components on the underside as many are unmarked, and as the PCB tracks are corroded I expect that many of these may be damaged.
It would be great if someone could find a schematic for this PSU. I don't think it can be directly replaced by another type of PSU as the connector is a different size and I am not sure if the wire colours would correspond with the standard voltages.
If anyone is interested I would be happy to post the photos I took of my machine.
I was hoping to get it working again as I really did like it when I used it. It had 1MB onboard RAM and 4 30-pin slots which I filled with 4x 1MB Simms, and it ran DOS/Win 3.1 without a problem, and was fast at the time.
I would like to get more information/help if any of you are interested.
I have a large collection of vintage hardware which I am planning to sell now I am retired, so if there is somewhere on this forum for that I will hopefully be able to post some items there.
Regards,
vikinggold