Built: Nov 7, 1989 (mainboard second half of 1984)
Mainboard: Rev 250425
CPU: 6510 (date code 2684)
SID: 6581 (date code 2184)
VIC: 6569R5 (date code 0989)
RAM: 64KB
“Breadbin” case
Trivia
Was sold as broken, only showing random letters when turned on.
Top and bottom shell of the case have different dates stamped (top: 1989-06-08, bottom: 1989-07-11).
Although it’s a C64G, inside there is a 250425 longboard. The C64G series was the last batch of C64 ever produced for the German market. I assume that Commodore just reused every spare components they could find.
It seems that the main board was built in 1984 for the NTSC market, and was then modified for the PAL market in 1989. While all other chips have a date code of 1984, the VIC chip has a date code of 1989, but was below the original metal shield that was firmly soldered in. I assume that in 1989, Commodore repaired this machine, changed it to PAL, and then sold it as new C64G on the German market.
Restauration Works
One case hinge was broken off. Fixed by a 3D printed hinged and glued it to the case.
Case and keyboard disassembled and thorougly cleaned. Some of the springs have been overstretched by the previous owner. For this reason, some of the keys need a considerable bit of force for pressing, while others feel normal. I tried to use as many of the overstretched springs for rarely used keys, but eventually also had to use some for standard keys.
Two rubber feet were missing, replaced with four new feet.
Replaced three dead DRAMs (U24, U21, U11). Diagnostics succeeded after that, but display still showed trash.
U14 was the only MOS standard chip. I replaced it with a 74LS258. This fixed the computer! Testing the MOS chip again brought back the display trash, so U14 was the culprit.
Found residues of thermal paste on all ROM chips, and cleaned them.
Removed all chips from the sockets. There was an oily liquid below the chips and in the sockets. The previous owner seemed to have used this liquid as contact cleaner. Tried to remove it with IPA, but it’s hard to get rid of. If the system should have stability issues later, I recommend to replace all DIP sockets with new ones. Only exception is the VIC chip, as it was still seated under the original metal shield. (There was even a dead bug hidden under the left CIA chip.)
Replaced all electrolytic capacitors with Vishay and Panasonic ones. An unmarked 100µF capacitor was removed. Also replaced all 78xx regulators with their respective Traco Power DC/DC converters.
Removed the metal shield of the VIC, in order to clean the area, and give the VIC a proper heatsink.
Thorougly cleaned the board. On the upper side there were residues of a dried liquid. Tried my best to remove it, then gave the board an IPA wash. I wish I had an ultrasonic cleaner to clean the board.
Applied heatsinks to CPU, SID, VIC, and PLA.
Full harness diagnostics reported a bad right CIA. I swapped both CIA chips, and the error was gone after that. When I removed the CIAs, there were still residues of that oily liquid, so I cleaned them again. I assume this was the problem.
Polarity of original power LED was reversed, it was also a bit dim. I replaced it with my “signature orange” power LED. LED clip wasn’t firm, so I used a new one.
Known Issues
Minor crack at the front left of the case.
Both screws on the right side of the mainboard are broken off.
SID noise is very silent on diagnostics, on all three channels.
