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How can I troubleshoot a Miniscribe 8425S hard-drive?

gregoireg

Member
I have a MacSE with an internal Miniscribe 8425S 20MB hard-drive. The drive has stopped working in 1990 and it hasn't been touched since then.

The issue is that the drive doesn't spin at all. There is no disk rotation when it boots.

I have opened the drive and both the PCB board and the mechanical internal parts look OK. See attached photos.

I have plugged my own 12V power supply and I see a pick of current around 750mA for half of second and then it goes down to 0. The voltage goes also down to around 10V. And it does it again.

In other words, it seems that the logic board tries to rotate the disk but it's not succeeding. I can manually rotate the disk. The 6-pin white connector on the side of the board looks OK. I guess that it's what powered the disk rotation motor.

I have seen some posts and videos about problems of the little side motor that pushes back and forward the arm but I don't think it's the issue I'm dealing with. My problem is no rotation of the disk.

Any idea or recommendation how to troubleshoot this drive?

(Ideally, it would be ideal to have a working hard-drive to test A/B between the PCB board and the mechanical part. I'm in the Silicon Valley.)
 

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gregoireg

Member
There is a morse-code error code displayed by the LED according to this page: https://stason.org/TULARC/pc/hard-drives-hdd/miniscribe/M8425S-21MB-3-5-HH-SCSI1-SE.html

Message Definitions
-------------------
Code 0 - Microprocessor RAM error
Code 1 - Microprocessor ROM checksum error
Code 2 - Interface chip diagnostic failure
Code 3 - Write Fault latch will not reset
Code 4 - Index pulse not detected during spinup
Code 5 - Unable to reach 3600 rpm in 600 revs.
Code 6 - Unable to stabilize spin speed in 10 seconds
Code 7 - Unable to maintain spin speed to 0.5%
Code 8 - Unable to uncover Track Zero sensor
Code 9 - Unable to cover Track Zero sensor
Code A - Track Zero interrupter misadjusted
Code B - Shipping zone error, crash stop misadjusted
Code C - Carriage stuck during recal error
Code D - Seek errror during burn-in or recal
Code E - No hall transitions during spin-up
Code F - Unexpected interrupt from processor

My error seems to be code E: No hall transitions during spin-up

Any idea what it means precisely?
 

gregoireg

Member
I have manged to boot and rotate the disk once but it doesn't seem to be reliable. Does anyone know where the hall sensor is located? Is this the little flex in the PCB hole between the main 3 chips (just on top of the center of the disk axis)? Has anyone tried to replace this sensor?
 

Phipli

Well-known member
I have manged to boot and rotate the disk once but it doesn't seem to be reliable. Does anyone know where the hall sensor is located? Is this the little flex in the PCB hole between the main 3 chips (just on top of the center of the disk axis)? Has anyone tried to replace this sensor?
The issue is unlikely to be the sensor, it is correctly identifying that the disk isn't spinning.
 

gregoireg

Member
I'm resuming this thread. I still have an issue with the drive and I'm 99.99% certain that the logic board of the drive is OK.

- Sometimes, the disk starts rotating and everything is fine. That happens 100% of the time if the drive was working in the past 5 minutes or so.

- sometimes, the disk doesn't start even after multiple boots. If I rotate the disk a few turns with my finger, usually the disk starts at the next boot.

It seems that the motor gets stuck after a few hours. Has anyone open the motor (German PAPST???) of a Miniscribe 8425S to put some oil or grease? Any Youtube video or picture?
 

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gregoireg

Member
Strange video but it's a little bit the same problem:
The comments seem to indicate that I'm not alone. I'm not sure how and where to insert oil... On the other side, there are the plates - certainly not a good idea to put oil on the other side along the plates.
 

bibilit

Well-known member
It seems that the motor gets stuck after a few hours. Has anyone open the motor (German PAPST???) of a Miniscribe 8425S to put some oil or grease?

common issue with those drives, i had a few having the same problem, no fix so far.
oil probably thikens with age.
you can try to keep it rotating for a while (using an external psu) hoping to improve things.
 

techknight

Well-known member
I have also seen it where the motor control/driver IC goes bad, and itll drop a phase. You know because when the motor tries to spin, itll only spin to the dead pole and get "stuck" there.

In other cases, it may start but itll sound a bit rough.
 
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