If they come up to the random-character screen (no
"*** COMMODORE BASIC ***"
banner)
I've run into about 1/2 dozen PET's over the years which have had ROM's go
bad. Seems to be a real problem with the devices Commodore used.
Often the symptom is as described above, sometimes it works "a bit" and then
dies (depends where the code is corrupted).
You can get most of the PET ROM images from the VICE simulator archive.
Regards,
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools:
www.dunfield.com
com Vintage computing equipment collector.
http://www.parse.com/~ddunfield/museum/index.html