Commodore 1541C repair
I bought a Commodore 1541C drive a while ago. It was sold as a faulty unit. The seller said it was broken, and that it makes chattering noises. The chattering noise is normal at power-up because the head is pulled back by the stepper motor and hits the end-stop, but he did also say that it didn't read disks. I have cleaned the heads, and it does read disks, however the motor never stop! The fault I have now is that the motor spins continuously. I measured motor control signals at the gate-array after the CIA IC, and motor control signal looks ok there. The signal is high at power-on and then goes low (stop) after the start-up sequence as expected. In the schematic below the motor signal from the gate-array comes in on one of the inputs of the inverter UC6. The CR10 is shorted by traces on the PCB, because UC6 is 74LS06 and not a 04 as it says in the schematics. This is because 06 has open-collector outputs, and therefore doesn't need a diode to isolate it from whatever comes