I have an Addams that was working fine (the sound board was one that i grabbed from a project machine that has not been powered up for probably 8 years - but worked fine for a number of weeks), then the sound became quite distorted - like it was playing underwater and very scratchy.
I have -
reseated ROMs, socketed IC's and ribbon cables heaps of times
replaced caps C15,36,38,20,23,46,47
Speakers are fine at 4ohm and pull in with a 9V battery
I'm wondering where the next place on the sound board is to look at replacing/fault finding - there seems to be very little repair information on these boards....