I found an Asus SP97V Pentium-I motherboard. It works with both AT and ATX power supplies. At least it's supposed to, because it actually doesn't.
I put a Pentium 120 CPU, four RAM modules and a Cirrus Logic PCI VGA into it to test. All of these work in a different mainboard. The power supply also works.
This board seems to be faulty. It doesn't boot, nothing appears on the VGA. The power LED doesn't turn on, and the connected PC speaker doesn't make any noise either.
Yet the CPU is getting warm, the CPU fan spins, and I can measure correct voltage anywhere I try.
What do you think might be wrong with this board? I'm fairly sure I set the jumpers correctly. Even if I didn't, the power LED is still supposed to light up, doesn't it?
I know, normally one should just throw away a faulty motherboard, but I'd hate to trash such a high quality vintage board if there's some hope to fix it.