I have worked on a few Ampeg PF-500 and PF-800 amps. Basically I just did a main board swap.
I know an electrical engineer who was on the team that designed those amps. He said those amps had good designs. The problem was they were built with the cheapest components in China. He also said that Loud Technologies would get broken warrantied amps back and just put a new board in. They would not bother to analize and find where the failure(s) were. Their QC sucked and it shows. The internet is littered with PF failure stories. It is too bad because they were decent sounding amps.....when they worked.
Is there a board I can put in my old broken PF 500 that is worth putting in there by chance?