Send me a picture of the 4mhz jumper area shown here: https://deramp.com/downloads/vector_graphic/hardware/Micropolis FDC Jumpers.jpg
What speed is your CPU running?
Mike
Here is the speed jumper area:
The crystal attached to the Z80 is 8mhz.
Send me a picture of the 4mhz jumper area shown here: https://deramp.com/downloads/vector_graphic/hardware/Micropolis FDC Jumpers.jpg
What speed is your CPU running?
Mike
Edit: The head mechanism is not moving at all. Belt & disk spins, but no head movement. Occasionally I hear a squeaking/squealing sound like something is trying to move. Could the stepper motor be seized?
Through rough handling in the past the leadscrew can actually pop out. Perhaps imagine a dislocated joint. Can you see that it is seated correctly at both ends. If you send the right signals you might get a tiny amount of movement when it is in that state.
Sounds like you'll have to start diagnosing drive operation then. Now that you have the unit open, do both drives spin when either drive is selected? With power applied, can you still rotate the worm gear on each drive with your fingers or does it feel like it's being held in place now?