Sometimes transistors and other silcon shorts and dies like so. It looks like the switching transistor of some voltage regulator gave up. Assuming no other problems, replacing the transistor and the close by capacitor will make things work again.

Tiido wrote on 2021-02-27, 16:22:

Sometimes transistors and other silcon shorts and dies like so. It looks like the switching transistor of some voltage regulator gave up. Assuming no other problems, replacing the transistor and the close by capacitor will make things work again.

Exploded power FET and melted inductor... smells like short-circuited low voltage power supply.
It had to be quite smoky.

I missed that inductor completely, yeah, there's definitely a short down the line somewhere...

froller wrote on 2021-02-27, 16:33:

Tiido wrote on 2021-02-27, 16:22:

Sometimes transistors and other silcon shorts and dies like so. It looks like the switching transistor of some voltage regulator gave up. Assuming no other problems, replacing the transistor and the close by capacitor will make things work again.

Exploded power FET and melted inductor... smells like short-circuited low voltage power supply.
It had to be quite smoky.

the house still stinks, Mrs isn’t happy she’s got all her Yankee candles on now haha.. I disconnected the PSU from the MB etc and it still seems to power up ok, I’ll have to check it with VOltmeter, wether or not I’ll risk using it again is another matter, I suppose it’s impossible to buy new AT Psus nowadays.

Thanks for the heads up on repairing, I’ll check into that, it’s probably easier to source the parts then find this exact socket5 mb

Scott8bit wrote on 2021-02-27, 16:18:

Well that was a short trip down memory lane, interrupted with the putrid smell of burning 🤣.

1. Check (with Ohm-meter) if melted inductor's rightmost (on photo) pin has direct connection to the ground. It should after all that damage.
Normally with all the stuff plugged into MB there should be at least hundreds of Ohms or more. I bet you'll read around 0.5- 2.5 Ohms.

2. Remove one by one every PCI device, memory and CPU checking if line is still shorted.
You either find who to blame or ensure you are screwed.

For a power supply, buy a nice, high quality ATX power supply and an ATX to AT adapter cable.

I refuse to use ancient AT power supplies when at all possible.

Newer power supplies output much cleaner power and have actual protection built in.