Tandon TM-100-1 electronics repair

On 04/27/2017 10:42 AM, Ethan Dicks via cctalk wrote: The issue with Jugi's artistry is that there isn't a single version of the PCB for the TM-100. I have drives with 3- 4- and 6-wire steppers on them, all taking different PCBs. But a TM-100 is a very simple-minded device. You can easily check its basic mechanical operation off the system by grounding various signal lines (all are active-low). So you can ground the motor line to make sure that the motor spins; you can ground the drive select to see if the LED illuminates. With the drive select operating, you cna use the STEP and DIRECTION lines to move the head carriage; you can check the operation of the track zero sensor. Checking the read-write channel is a bit more challenging and a 'scope can be very useful. For lack of anything else, if you've got a PC with a floppy controller, you can use Dave Dunfield's ImageDisk utility to perform simple checks. He includes an RPM tester, though if the drive still has the strobe disk attached to the spindle flywheel, a simple line-operated neon lamp can do the same. --Chuck