They are transistors and may have failed, you can check their output voltages with a multimeter.

RBretrox wrote on 2020-02-03, 13:13:

However, I'm usually sat on this shiny smooth plastic chair that I'm convinced gives me a static charge, when I slide off it to go and unplug some cable in the machine. Could be that, as my son knows too well when I give him a shock when he's playing a game on a computer next to me!

I wonder why no one took up on that so far...

I'm not sure if you are aware of, but even the slightest static discharge will damage or even destroy semi-conductors. You should stop sitting in that chair while working on computers and also start wearing an ESD protection wristband. I can actually see how the board died if you handle that stuff this way.

Good point and something to act on

Honestly I doubt that. I’ve bought bare motherboards from eBay that showed up wrapped in plastic wrap and stuck in a box of styrofoam peanuts. Someone will throw out the “you never know what damage has been done” but, and while true, it’s a little like proving the existence of God to and atheist. You’re both going to find evidence and none of it will be, nor can be, conclusive.

I’m not saying proper static prevention is not a good idea, but flat out component failure is usually something a little more obvious.

I aldo dont think this sounds like static damage failure but tbh I wouldnt try any harder to diagnose and fix a S370 board they are fairly common.

Possible answer...

Tried another PSU, powered on and we have the magic smoke and fire!

This is now fully burned out, so I'm going to remove both and try to find replacements

Small consolation, I soldered the PS/2 ports back on.

RBretrox wrote on 2020-02-08, 18:51:

Possible answer... […]
Show full quote

Possible answer...

Tried another PSU, powered on and we have the magic smoke and fire!

This is now fully burned out, so I'm going to remove both and try to find replacements

Small consolation, I soldered the PS/2 ports back on.

Ahhh you need to find out why it burned. Are you using some not supported CPU ? Possible a bad cap caused that but more likely human error.....

That's true.

It's a low cost part, so I may as well give that a go

appiah4 wrote on 2020-02-08, 08:35:

I aldo dont think this sounds like static damage failure but tbh I wouldnt try any harder to diagnose and fix a S370 board they are fairly common.

I'm keen to fix it as I want a motherboard with AGP, PCI and ISA for a Windows 98 project machine and these boards currently seem to cost more than I'd like to pay. Seen the same board recently for £50 on eBay.

I also like fixing stuff, as long as the repair parts are not too costly.

Bit of a twist here

Browsing eBay and I find exactly the same obscure motherboard as the broken one.

It was far too much money.

Offered £30 plus £5 postage and it's mine.

So even if the repair doesn't go well, at least my project can be back on track