I've done a bit more work:
I replaced all the capacitors on the power supply board. The hum is still there, but is quieter. It got quieter when I replaced the four larger caps (C705-708). However, I put back in the original four and it was still quieter. I know that's weird. Since the large caps on the electrolytic board are rather expensive, I can't justify replacing them as a guess right now. Especially when it seems more like a grounding issue.
I'm really having trouble finding any potential pinched, broken, etc. wires or problematic solder connections. Any tips?
I replaced all the capacitors on the power supply board. The hum is still there, but is quieter. It got quieter when I replaced the four larger caps (C705-708). However, I put back in the original four and it was still quieter. I know that's weird. Since the large caps on the electrolytic board are rather expensive, I can't justify replacing them as a guess right now. Especially when it seems more like a grounding issue.
I'm really having trouble finding any potential pinched, broken, etc. wires or problematic solder connections. Any tips?