PowerBook 100 in chime loop

[all2coolnick]

I have a PowerBook 100 that powers up but chimes about twice every second indefinitely until power is removed. I’ve replaced all the electrolytic caps and tested in another fully working PowerBook 100 so it’s definitely the logic board. I’ve inspected for any damaged components or corrosion but beyond that I’m stuck. I have the schematic but I don’t understand the POST process to even guess what could cause this symptom.
Could anyone offer any pointers?
Much appreciated.

 

[alexGS]

When you said “tested in another fully working Powerbook 100”, did you mean you’ve tested the power adapter, or the RAM expansion? Or the hard drive?

After the chime, there’s usually a RAM test (takes longer with more RAM installed, I have a machine here with 8MB total that takes about ten seconds), and then the hard drive spins up. If it’s not a RAM fault, my guess is that the hard drive might be drawing too much power and dragging the voltage down to cause a restart.

The good news is that logic boards probably aren’t scarce now that LCDs are damaged or dying from corrosion etc. I have about three spare here.

Also have a final check that no caps are in backwards or wrong places particularly the two around the reset button area; if they were wrong value (10uF instead of 1uF), that could cause a self-repeating reset perhaps (normally it charges up and delays the line while doing so) although I am clutching at straws with this last guess.

 

[all2coolnick]

Thanks for the advice. I’ll look into the things you suggest.
Regarding my comment about testing in another fully working PowerBook, I meant I fitted the problematic logic into another PowerBook 100 that was working i.e. every other part except the logic was known to be good. The chime looping happens with no HD connected.
There is no interval between the chimes. It just plays the chime sound back to back continuously.
I should also mention that it was doing the same thing before I recapped the logic.

 

[Foldedtoad]

Was this chiming issue resolved? I have a PB100 which is showing the same symptoms: hard cycle of chiming.
I have tried the suggestions above, but no results.