First post, by aitotat
I have a Soyo SY-5SSM/5 motherboard but it does not work. The problem is that PSU won't start. I tested that the motherboard is not shorted and I was able to follow the soft power button header to one leg of the SiS 5595 south bridge through a 1K ohm resistor (and the other pin of the header was ground). That was OK so the problem must be between ATX stand by power and SiS 5595 south bridge.
The board is bend a little. Not even a worst case I've seen. I can get the board started if I push down the corner close to the ESS sound chip and the opposite corner close to VRMs. Then the power button works and PSU starts but stops (repeats few times power on-off) when I stop pressing down the corners.
So there must be a bad contact somewhere. I already re-soldered through-hole components (excepts bus slots and other connectors) but that did not help at all. So the problem must be on the top side and 5595 south bridge is my top suspect since it has lots of very tiny legs and it is in the area that bends when I press down the corners. But I did not find any loose legs and I don't feel comfortable to resolder it just in case. That needs to be the last thing to try since I might destroy the board while doing so.
So what else is involved in soft power on? I tried to read the 5595 datasheet but if I understood correctly, it pretty much is responsible for the powering up.