800K Floppy Continuous Clicking Stepper Motor

[managerhumphry]

Working on salvaging a Macintosh 128K. System powers on fine and displays the floppy logo, waiting for a disk to bootup. However, the Sony MP-F51W-03 floppy drive did not work. Disassembled it, cleaned and relubed everything and replaced the eject gear. Now the eject mechanism works nicely but when the system is powered on the the stepper motor just runs the head forward to the end of the worm gear and it clicks loudly.

Check out the video:

800k clicking.mp4

drive.google.com

There's another somewhat similar thread here where a few other people mention having a similar issue. Anyone have suggestions of what to try?

Thanks!

 

[LaPorta]

What color stripe wire does it have? Is this still a 128k? The presence of an 800k drive indicates it either had a ROM/RAM upgrade, or had a logic board swap in the past to either a 512k or a Plus.

 

[managerhumphry]

Yellow stripe on the floppy wire.

 

[alexGS]

Do you have a 400K drive or an 800K drive? Now I’ve seen the video - it appears to be the 800K drive, and the problem I’m familiar with, except yours is hitting the head is at the outer end of its travel.

First, use a toothbrush or similar to make sure there’s no dust blocking the sensor.

It seems the stepper motor has to reverse direction when the sensor is triggered, then it stops when the sensor is un-triggered (ie. when the flag leaves the sensor). If the sensor is not being un-triggered, that might explain why the head movement doesn’t stop.

Otherwise, if the stepper motor is in the wrong position, that seems to make a difference because it causes it to over-run. You might try turning it slightly. This does affect alignment, but then, if the heads won’t stop moving, the drive can’t be used anyway.

I would start by cleaning and possibly replacing that track-0 sensor. It seems to be stuck ‘triggered’. Re-do its solder joints too.

 

[volvo242gt]

The zero track sensor can be adjusted. Loosen up the screw, then move it slightly, until the drive operates normally. The stepper motor will probably still need to be adjusted, though.

-J

 

[alexGS]

I meant stuck at the inner end of head movement. Head should have moved outward, triggered the track-0 sensor, then moved inward to un-trigger the sensor, then stopped. It hasn’t stopped, seemingly because the sensor is still triggered. Definitely try cleaning the sensor first before moving it and losing the alignment. Also consider trying another drive controller board or trying to measure the sensor output.

 

[volvo242gt]

https://tinkerdifferent.com/threads/superdrive-floppy-maintenance.549/post-5174

See TinkerDifferent thread. I've successfully been able to get drives to work by adjusting the sensor (not the head).

 

[Phipli]

Is there a chance you got grease in the sensor?

 

[managerhumphry]

No grease on the sensor. I checked it under microscrope (while still installed). I tried brushing it and blasting with compressed air to clean any dust, no difference. I also tried adjusting it's position ever so slightly, but still have the same behavior.

 

[managerhumphry]

By adjusting the stepper motor position I assume you mean just loosening the screws a bit and wiggling it around to reposition it slightly? Tried that too.