I'd be a little bothered that this is happening next to that MC34063 which is a buck/boost regulator, so it can step up voltages. Not sure how it's being used in this circuit (programming voltage for EEPROM?), but it might be worth checking any voltages on it before plugging another PROM in. I know the trace is only burnt looking after the dear departed D21, but the current to do that had to come from somewhere, probably on the two traces coming from the regulator.

Well repair hasn't gone well. I am not sure what the values of the shorted resistor are to find the correct replacement. Does anyone have the same board to measure the values it has?

It is still a 0Ohm resistor.
Replacing only the resistor will likely not help you since something else must have caused an overcurrent event that burnt the resistor.
snufkin gave you a good lead with pointing out MC34063.

Yep. If it looks like something leaked, it wouldn't have been a zero Ohm resistor (aka an SMD jumper wire). Nothing in there to leak. Plenty in that cap.

Problem with that cap theory is its position, it would have to leak against gravity.

It looks like MC34063 is driving Q17 Q18? and pin 1 where that resistor seems to connect also provides main power to the transistors.
Geofand26 did you by any chance forced CPU in wrong orientation and powered the board?

Geofand26 wrote on 2022-01-28, 09:06:

What do you mean by "the capacitor is shot"?

So I'm not native english myself, but I'll try to explain anyway how I see it.
It's basically a way to say that something broke and isn't working anymore.

For instance if you were to shoot a human, then that human will not work properly anymore afterwards (usually because the human will be dead in some way causing it to malfunction).
But saying "x is shot" is just a different way for saying "x broke and is no longer working anymore" or "x has gone totally defective" or "x is not responding anymore to any input" or just "x is dead".

Something like that 😜

rasz_pl wrote on 2022-02-09, 23:29:

Problem with that cap theory is its position, it would have to leak against gravity.

It looks like MC34063 is driving Q17 Q18? and pin 1 where that resistor seems to connect also provides main power to the transistors.
Geofand26 did you by any chance forced CPU in wrong orientation and powered the board?

I was wondering something like that, but I can't figure out why that trace would get hot. I had it wrong before, and thought that trace was an output from the switch controller. But I couldn't make it make sense with the datasheet. Now I think that trace is a 12V supply to the switch controller (maybe routed from the nearby fan header), to give it the drive strength to turn the FETs on and off quickly. But it should be protected from a short on the CPU by those FETs, I thought it would only be driving their gates. If it started switch too fast then maybe it'd draw enough current. But wouldn't a CPU short just cause the high side FET to be on all the time, so the area around the FET would would burn, but not the 34063? There's a timing capacitor on pin 3 that controls the switching speed, but that look ok.

I think the circuit is probably similar to page 7 on the datasheet: https://www.onsemi.com/pdf/datasheet/mc34063a-d.pdf, with the external PNP option replaced by a nFET (Q18, using 12V to switch it, so Vgs is large), and what I think is a big diode at Q17.

rasz_pl wrote on 2022-02-09, 23:29:

Problem with that cap theory is its position, it would have to leak against gravity.

It looks like MC34063 is driving Q17 Q18? and pin 1 where that resistor seems to connect also provides main power to the transistors.
Geofand26 did you by any chance forced CPU in wrong orientation and powered the board?

Nope. But now that I think about it I did turn the board really quickly and I am using an AT style power supply so maybe?

can you elaborate "board died"? no beeps nothing?
do you have a multimeter? do you know how to measure stuff?

take it out of case, unplug everything, no cards no cpu no ram, only board and psu, AT supply black wires go together in the middle
plug black meter probe to molex connector middle hole (black wire, ground)
turn it on and with the red probe measure and note down voltages on all the pins of Q8 Q17 Q18, four corners of BIOS socket (unless you know which pin is 32, then only that pin) and both sides of both big inductors (round things with red wire coiled around them), be careful not to short anything with multimeter probes

Good news. Board is fully working again! Resistor was actually fine but the trace really was broken. Used a wire and now it works fine. Thank you everyone for helping find and fix the issue. I hope I will be able to use the board for a lot longer now.

Oh and btw got a new CPU for it as well

Awesome, thanks for the update! 👍