according to this:
https://forums.atariage.com/topic/11...problems-pics/

it looks like a cap replacement fixed it, also would be a good time to do the audio mod so it doesn't hum so much too.
later on down the line (page 2) it looks like some one had to replaced a op amp too, both shouldnt be too hard i imagine.

i do remember these being poorly soldered to begin with so i'd probably start out checking for bad joints since its free