This sounds like a power supply problem -- the extra load of the tape drive motor is pulling the unregulated supply down, which is then causeing the 5V line to drop too low. Many PETs have a white Molex 0.156" power connector on the mainboard, the socket part of which is wired to the transformer and smoothing capacitors mounted seprately in the case. This connector is somewhat under-rated, and tends to go high resistance and overheat. If the plastic has started to turn brown, this is one of your problems. Either replace the connector, or remove it completely and solder the wires directly to the main PCB (you might then want to add an in-line connector of a suitable rating to aid future servicing). Also, check the smoothing capacitors (particularly the large ones mounted off the main PCB). It's possible one of those has dried up. -tony