Originally Posted by kipper2k
All my A600's have been recapped and are what i consider to be in reasonable to good health but chip temps vary from machine to machine. I think age is a factor and just looking at how clean a computer is, is not a reliable indicator of the motherboard itself. It is a bit of a crapshoot with these machines as to how well they behave, with its basic config they will probably chirp along forever but putting extra stress on them could be too much for some of them.
Temperature differences in the CPU are probably related to the manufacturing process. Impurities in the production of the CPU cause CPU's to have a higher temperature. Which is still true today with all modern CPU's.
So at the time there was probably a wide temperature range in which a CPU was working and validated as OK. But if you now stick something over it the temperature goes over that tolerance level and errors occur.
An option could be to replace the 68000 with a different one.
On a side note. I have 2 ACA620 here. I have a rev1 Amiga 600 here in which neither worked. I didn't check why because I just stuck them in 2 other Amiga 600 in which they worked immediatly.