Decoupling capacitors

[Zac67]

Yes: capacitors - apart from electrolytic ones - extremely rarely break. If they're not short they're most probably OK.

What is the problem with the board? Does the 500 run at all? Is the RAM recognized? Does Amy crash?

[Zac67]

4.78V on the A501 might be a bit low; if you measured the PS input it's way low - why don't you juice up the PS .2 or .3V?

If it's not voltage I'd guess one of the RAS, CAS or WE lines is dead, so the RAM can either not be addressed or not be written to...

Yes, dead RAMs most often get warm pretty fast.

[Zac67]

Still not working?

Voltage is not really awsome, but should work.

Well, if one chip is bad, Amy might see the error on memory sizing and doesn't add the memory at all. More probable though is the missing _EXRAM signal on pin 32. Is that grounded when the expansion is plugged in (I assume it's a non-ECS 500 w/ 512 KB chip and 512 KB pseudo fast ('Ranger')).

PS: bad chips get hot VERY fast - IF they get hot