I had similar problems on the past.
In fact, it was a problem with the socket itself, that I could only spot by testing it with the connected IC and touching the probes on the top part of the IC's terminal and in the botton of the board.
I never had a fried CPU or PPU from just removing it from the board, but maybe you could try some clone CPU/PPU pair, try searching for UA6527 and UA6528. They're NTSC clone CPU/PPU respectivelly. Unfortunatelly they have some issues
I've found some clone pairs cheap here
The real thing is pretty more expensive, here
A wish you the best!!