Need help fixing stepper motor issue with Disk II floppy drive

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Magnificat's picture
Last seen: 2 hours 45 min ago
Joined: Mar 16 2020 - 12:53
Posts: 26
Need help fixing stepper motor issue with Disk II floppy drive

Hi All, I have a Disk II floppy drive that was purchased a while back and was NOS at the time but of course arrived DOA so i started troubleshooting it a whlie back. I have a working disk II here i use as a test machine to move parts/boards, etc..

What it's doing is.  on turning on the machine the stepper flapps a bit, and the primary motor spins the disk but the stepper motor never engages and starts moving forward/reverse to any tracks on the disk. 

What i have done so far.... 

1. moved the logic chips from working system to non working. no change.

2. moved the entire top main board from working to non working, both boards work on the working disk II drive.

3. removed the stepper board on the back of both and swapped and both work on the working disk ii drive.


So i assumed it would end up being the board on the back but after intalling the NOS board to old drive it works, so seems all electronics are OK.  Is it possible that the stepper motor itself is the problem?  It engages OK.  I could swap the motors on the drives but at that point my NOS drive won't be NOS anymore but a frankenstein of parts..

So just asking if anyone has seen that before and if there is another place I could look for the culprit? I think i have exhausted most of my options so far..  thanks in advanced!
Last seen: 1 day 9 hours ago
Joined: Apr 26 2016 - 08:36
Posts: 33
It sounds like you've

It sounds like you've emliminated most possibilities and traced the problem down to the stepper motor itself.


What I'd look for now is if the stepper motor is seized in any way.  Does it turn freely when you disngage it from the slide carriage?

Are the wires from the stepper motor to the analog board intact?  Is the internal edge connector intact?


Knowing that the electronics aboard your non-working drive all check out and the spindle motor appears to be working you should be concentrating on the connections between the stepper motor and the card.  And making sure it turns freely.

You can also connect it as drive 2 and run a program like Aptest or another drive utility that checks drive speed.  Those speed checking routines usually move the disk drive's head to track 16 or thereabouts.  That's a good test to see if your non-working drive can spin the motor reliably and force it to move the stepper motor.




Last seen: 11 hours 30 min ago
Joined: May 27 2009 - 01:37
Posts: 966
When I had that issue I

When I had that issue I cleaned all the contacts on the analog board and the wire/connector itself. Fixed it right up.

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