In his latest video, Root42 takes on another 1541 drive repair, this time facing the familiar issue of a drive that powers up but never stops spinning. From the moment the power light comes on, the drive motor whirs endlessly—a classic sign that something is wrong on the board. Instead of guessing, Root42 opens it up to diagnose the real cause.
Inside, he finds a mix of original 1984 MOS chips and later replacements from Rockwell and UMC. The first suspicion falls on the 5V line. A quick voltage check confirms there’s no 5V reaching the CPU. That narrows the problem to a failed voltage regulator or bridge rectifier. Using a multimeter, he tests both and finds the regulator likely at fault.
Testing, Troubles, and Some Surprises
Root42 carefully removes the 7805 regulator and tests it outside the circuit. The output shows around 10 volts instead of 5—a clear failure. After replacing it with a working spare, he checks the board again. The drive now has a stable 5V supply, but it’s still stuck spinning. The mystery deepens.
Digging further, he traces the issue to the reset circuit. Using his oscilloscope, he finds that the CPU reset line never goes high, meaning the CPU is held in permanent reset. By isolating components in the reset chain, he discovers the LS14 inverter chip has failed. Once that chip is replaced, the drive finally wakes up and behaves normally.
Testing and Final Results
With a new CPU, new LS14, and proper 5V regulation, the 1541 runs flawlessly. Root42 tests it with an alignment and speed calibration, showing 300.2 RPM—right on the mark. He notes that drives with the Alps mechanism are particularly reliable, while Mitsumi models tend to develop head issues.
After a long troubleshooting process, the once-dead 1541 is alive again, spinning only when it should. Root42 wraps up the video with his trademark humor and invites viewers to follow his future restoration projects.
