Slightly out of topic question

[Jay Martin]

Usually removing a cartridge while the unit was on would cause the power
supply to spike.  The C64 used a 7805 type regulator that does not contain
protection for this.  What usually happens is the power supply suddenly
decides to oscillate at around 8 volts.  This then fries most of the RAM
chips (they didn't have much protection in those days).  You will probably
have to replace the power supply and the RAM chips.  But try just the power
supply first.  Believe it or not, even though the power supply is
non-fixable (unless you got a real early one) and has a "brick" of epoxy
covering all the components (causing the eventual demise of the regulator
due to it's inability to dissipate the heat) they then put a FUSE in there
(in the middle of the epoxy).  It **COULD** just be that blew..but you will
most likely not be able to replace it (unless you have some solvent to eat
the epoxy away.)

Try the power supply and then the RAM chips.

Jay Martin
P.S. I speak from a ton of experience, I used to work as a repair tech for
Commodore equipment.  



> -----Original Message-----
> From:	gronda_a at starnova.it [SMTP:gronda_a at starnova.it]
> Sent:	Monday, October 05, 1998 4:53 PM
> To:	synth-diy at mailhost.bpa.nl
> Subject:	Slightly out of topic question
> 
> Hello, I've got an old Commodore C64 (that it's also in some way an
> analogue synth!) to repair.
> Does anybody know what get fried pulling off a cartridge while the unit
> is powered on?
> 
> Thanks.
> Andrea