Ijack said:
Sounds like a problem with the main logic board, or possibly a hard disk error. But, then, it could be the power supply or even overheating because of build up of dust or a failed fan.
I think you need to have it looked at by someone familiar with Mac hardware (if you think it is worth the cost).
Thanks for the reply.
I think it has to be the mother/logic board.
I opened it up, removed all dust, and also removed and tested the hard drive and it's fine.
Given the logic board prices in the secondary market, I guess it's not worth it to try to restore this unit... It seems like it will cost 1/3 of a brand new iMac...
I suppose just keep the hard drive and the RAM...?