In this detailed repair session from the More Fun Fixing It channel, a returning Commodore 64 from an earlier triage video lands back on the bench. The issue? A suspected faulty Commodore 64 CIA chip—and possibly more. Initially working after a previous attempt, the machine now displays a black screen. Paul, the host, investigates the CI2 chip, which appears to have failed, and prepares for the unenviable task of desoldering a soldered-in CIA.
Diagnosing the Fault
Using a diagnostic harness, Paul confirms the CIAs are not counting properly, a clear sign of failure. But the fun doesn’t stop there—the system is also missing video output. Voltage checks reveal intermittent power, pointing to a temperamental power switch. After wrestling with a long screw and brittle plastic posts, Paul disassembles the switch for servicing.
The repair process is tricky. Desoldering proves frustrating, with fragile pads lifting off the board. Still, Paul perseveres. Inside the power switch, contacts are cleaned, lubricated, and rebuilt using fine sandpaper, contact cleaner, and silicone grease. Reassembly requires careful realignment of the switch legs and tabs, finishing with a confident click that tells him it’s back in action.
Socket Trouble and CIA Testing
But the mystery isn’t over. With the switch now working, the machine still misbehaves. Paul finds the power socket is loose, possibly contributing to intermittent faults. Replacing it brings stability, but the original CIA chip still fails diagnostics. Temporarily borrowing one confirms that both CIA sockets now work fine.
After reflowing solder, testing voltages, and swapping chips between sockets, the machine finally boots properly—with both CIAs responding. The keyboard and case clips have already been repaired in a previous session, so this unit just needs reassembly.
Conclusion
This is a classic example of how issues on the Commodore 64 CIA lines often involve more than just one fault. Paul’s careful testing and methodical repairs make for an instructive and satisfying video. If you’re into retro hardware restoration or just enjoy seeing stubborn faults get resolved, this video is worth watching.
