Commodore PET repair guide?

[Uzumaki]

I haven't had the chance to check out my latest aquisition, a $25 SuperPET 9000 but I couldn't find much detail on this with Google. If the problem is not due to loose chips or cables, then what can I do? The symptoms:

 

sometimes it boots up OK, sometimes it boots to garbage screen. When it boots OK, half of the keyboard doesn't work. I am quite sure it's the famous Chip Creep problem but if that's not it, then what? SuperPET 9000 is basically 8032 with numerous extra hardware added in, a RAM board, beefy CPU, a chip upgrade board whose function is unknown and that Commodore never talks about, etc. Schematic for power and monitor are easy but the mainboard is another beast.