I love bodges, man. Real engineering right here.

Last minute fix, mostly.

Double post- please delete

Hi all,

So I've replaced all surface mount caps with radials.

Unfortunately, I can't get it to boot. The Power supply spins up and there is no display.

I've tried:
Three other AT PSUs
A tseng Et6000 on the daughterboard (pci)
An ISA video card
Two other monitors

The best sign of life I can get, is if I remove all but one stick of RAM, it beeps 3x long.

Would appreciate any hints of where to head next as it's driving me nuts.

Thanks

This PC requires two EDO sticks 60ns matched set. Parity not needed.

The motherboard looks like an Intel Advanced/MN (Morrison32).

pentiumspeed wrote on 2020-06-22, 00:19:

This PC requires two EDO sticks 60ns matched set. Parity not needed.

Thanks Pentiumspeed. I have tried just about every combination of the memory I've got- looking at the "Installing Options in your personal Computer" supplemental manual, am following the dimm bank/pairing guide, with different combinations (1/4 RAM stick is not matched, so not using that in the testing). Still no result.

Have peeled off the top sticker, and the RAM has the following information:

B126LCEOMVP 74G1300 TOR 511
8MB 2M X 32 70NS 5.0V V347
FRU: 92G7245 OPT:92G7246

Looking it up, this should be indicated for the PC-350. I've reason to believe it is the original RAM for the PC.

Thanks as well, Windows9566. I'll see if I can dig up anything more about it.

Here is my IBM 350 200mmx for reference but the motherboard appears to be different. Maybe a newer version of the 350.
IBM 350 Personal Computer / 200mmx

Did it work before you replaced the caps?

Hi Intel486dx33; what a beauty. Looks very similar. These things are becoming quite the rarity. I notice yours also is suffering corrosion; took three days to remove the bulk from mine. Nothing a good coat of enamel can't fix.

chrismeyer6: unsure- there was so much of that "greasy" dirt clogged in the PSU + board that I wasn't willing to risk it. The PSU tests fine on other AT PCs, and so does the RAM. External video card doesn't change the outcome.

So, after many days of troubleshooting, jumper changing, cleaning, de-rusting & research, it's finally working. I'll leave the solution here for anyone facing a no-boot issue with their IBM:

http://ps-2.kev009.com/pcpartnerinfo/ctstips/93e2.htm

Here you'll find an IBM Service Hints & Tips document, containing the board layout and jumper settings (edit- it would be really awesome if someone could somehow archive this whole site!).

I found this document whilst trying to understand why there is a single "beep" when the bios is reset- indicating a partial boot.

For this model, the solution was to match the SW1 switches configuration with the processor, which was incorrectly set. This involved taking it off, carefully removing the heatsink with a craft knife to find the specifics.

For the Pentium in this machine, the correct settings involved setting the L2 cache to 0 with SW1 on, and changing VRE Enable (J9C1) to standard voltage.

It's alive:

Booting into BIOS:

Incomplete, could use some paint, but there you have it. All the best and thanks for the help everybody.