IIci boot issues - makes crackle then turns off

  • Board Nominations
    Nominations have now closed and the results are available here.
  • Hey Guest, MARCHintosh 2026 is upon us. Check out community projects, join GlobalTalk, and have fun!

Durosity

New Tinkerer
Aug 8, 2022
5
0
1
I have a IIci which is causing me bother. It was working several years ago before I removed its capacitors and stored it ready for a re-capping, which I've only just got around to doing. When I turn it on it does power up for a moment, the LED light flickers, the speaker makes a bit of a crackling sound, then it turns off. It's only on for 1-2 seconds.

So far I've tried the following:

Known good PSU (tested with another IIci)
Confirmed all caps (tantalums) have been installed correctly and in correct orientation
Swapped UC13/UD13/UE13 with chips from my other IIci, same issue on faulty system, other system working fine as it was,
Removed and cleaned up the sound chips which did have corrosion under them but no sign of any damaged traces or vias (same for the above UC13 etc chips)
Tried a different ROM in the rom slot.
Replaced ram modules

Anyone have any insights that could be causing this behaviour? I've had problems with the soft power circuitry on a Iicx before, but that just resulted in nothing powering on at all.