Hydrohs wrote on 2021-08-06, 18:57:

Ah, got them mixed up. Thought EDO predated FPM. Tried with some FPM RAM but made no difference. Removed the RAM and plugged in a (known working) speaker, and nothing. Speaker gets power but makes no sound. I also tried the CPU in another system I have just to make sure it didn't die in the process and it is still working. Got a POST card on the way which hopefully will help. The only other thing of note I can think of is that I have no battery installed whatsoever, not sure if that would make a difference on a system like this or not.

Did you installed two sticks of FPM memory or One? You really need two of those sticks installed to get it working.

A single 72 pin FPM SIMM should be enough for a 486, Pentiums do require modules in pairs due to the 64 bit bus. In fact my own GA-486VS works perfectly with a single module.

Do any of the chips feel uncomfortably hot when you power the board? All the chips should be only barely warm when running, except maybe your 486SX which should get a little bit hotter and the regulator. Also, check that the voltage regulator is not dead, when configured for a 5V CPU like yours the output pin will probably be shorted to the +5V input to bypass regulation, but if it's blown it could still be causing problems.

I'll try to check the jumper settings on mine as soon as I can, even though there may be slight differences due to the board revision.

None of the chips get super hot, the only ones that get noticeably warmer is the CPU, and to a lesser extent the larger SiS chip. For the voltage regulator, I think it's working as intended but I'm not 100%. If I'm looking at the datasheet correctly, pin 1 (leftmost in all my pictures) I'm measuring 3.2v, with pin 2 and 3 at 5v.

what comes to mind spontaneously, should the reset LED on the POST card go out shortly after the mainboard was started? or did I understand something wrong?

JimWest wrote on 2021-08-20, 19:55:

what comes to mind spontaneously, should the reset LED on the POST card go out shortly after the mainboard was started? or did I understand something wrong?

It does, reset only lights when board turns on (then turns off) and the same behaviour when power is cut. Sorry if I wasn't too clear on that.

Oh ok. If the reset mechanism already works, it's a start. 😀 had you checked the board for loose pins? especially on the pins on the chipset?