Over on the More Fun Fixing It channel, another Commodore 64 lands on the workbench for repairs. This particular machine has already been through the triage process in a previous video and was temporarily revived, but it’s back again—this time with no video output. That’s never a good sign.
After an initial assessment, the prime suspect is CIA Chip U2, which, unfortunately, is soldered in. That means it’s not just a simple swap—it’s a bit of a job. But before diving into that, there’s something else to address: broken case posts and a suspiciously long screw that’s making disassembly more frustrating than it needs to be.
Diagnosing the Problem
After finally getting into the case, diagnostics reveal that one of the CIA chips isn’t counting up properly. This confirms a bad CIA, but before pulling out the soldering tools, it’s time to check the basics—like power. A quick voltage test shows something unusual: the 5V line seems fine, but the 9V line is either weak or nonexistent. A little experimenting with the power switch—flipping it on and off repeatedly—suddenly brings the machine back to life. That’s a strong hint that the power switch is the real issue here.
Fixing the Power Switch
The switch gets removed, and, as expected, it’s full of gunk. Years of oxidation and carbon buildup have affected the contacts. The inside of the switch is carefully disassembled, and each contact is cleaned with fine sandpaper, contact cleaner, and a bit of silicone grease to prevent future issues. Once reassembled and soldered back onto the board, it’s feeling much more solid. Time to test it again—powering on the C64. It works! But… not so fast. There’s still another issue lurking.
The Faulty Power Socket
While the switch is no longer a problem, moving the power socket around causes flickering. That’s not normal. The socket itself feels loose, so it’s likely that the internal connections are failing. With no hesitation, the old socket is removed and replaced with a new (well, “new old”) one. This one has a much firmer connection, and, thankfully, no more flickering.
Replacing the CIA Chip
Back to the original issue: the faulty CIA chip. A borrowed working CIA is installed to confirm the diagnosis. Sure enough, the machine powers up with a cursor, and both CIAs are counting up as they should. That’s a solid fix. Now all that’s left is to track down a permanent replacement for U2 and wrap things up.
Final Thoughts
This C64 had multiple problems, but each one was tracked down and resolved systematically. The power switch was cleaned and serviced, the faulty power socket was replaced, and a failing CIA chip was confirmed as the final issue. With everything back in place, this machine is almost ready to return to its owner. It just needs a replacement CIA, and it’ll be back to full functionality.
