I have a Classic II with a couple of issues.  Before washing and recapping it, it would boot maybe 20% of the time, and otherwise would give a checkerboard pattern.  If it did boot, it'd run fine except for sound, which was intermittent, and terribly distorted.
 
Based on what I'd read on this forum, I washed the logic board gently (lots of hot water, using a q-tip dipped in alcohol where there was obvious buildup) and I replaced the caps.  I'm afraid I messed up C4 (a 47 uF electrolytic) and the pad separated from the track.  I tried to trace the contact back to another spot on the board, but no luck.  
 
Unfortunately, the problems haven't improved much.  Booting is quite a bit more reliable, but still not 100%, and sound is still completely messed up, though I'm pleased that C4 doesn't appear to be critical to the machine functioning.  So my remaining questions are:
 
- What does C4 do?  Is it sound related?  Is U1 an audio amp?  Any advice on getting this cap back into the circuit?
- I used MLCC caps where possible--I didn't see any reason why these wouldn't work, but are there any known issues?
- Was my washing maybe too gentle?  I've read about scrubbing and dishwashers but I was quite a bit more conservative than that
- What's my next step if I've already tried washing and recapping?
 
Thanks!