Miniscribe 8425SA 20mb SCSI HD flywheel permanent fix?

[bretwashere]

Hello all,

I own a Macintosh SE FDHD with a 20MB Miniscribe 8425SA SCSI hard drive. The drive did not spin up, giving a Code E error via the LED. In my other thread, I was advised to remove the circuit board and give the flywheel a spin. After adjusting the "interrupter" a few times, the hard drive was functional was was able to read from it.

However, once I power down the machine, I run into the same issue of the flywheel not spinning up, causing the hard drive to not function. For me to get it running again, I have to open up the Mac SE, remove the hard drive, take out the circuit board from the HD, and spin the flywheel.

Is there a more permanent fix for this hard drive? I really do not feel like disassembling the system and going through all that hassle just to have a working hard drive. Thank you.

 

[MacTech68]

I'm wondering if the flywheel can be removed to see what is accessible beneath. There may be a braking mechanism or a bearing accessible.

I'm leaning towards a bad bearing that MAY like a TINY drop of oil. These drives bearings were pretty noisy even 10 or more years ago. I just can't recall if the flywheel is easily removable. If you manage to get it off I'd suggest a light cleaning of the dust with a fine brush and vacuum cleaner suction to prevent any particle ingress into the bearing when a drop of oil is added.

I also can't recall if the flywheel is factory balanced. If you see what appear to be small indentations drilled out of the flywheel at various locations then that would be an indicator. In which case, you'd need to be able to re-align the flywheel with the motor shaft reasonably accurately upon re-assembly.


Otherwise I think you'd be looking at major surgery, removing head-pack, platters, flywheel, hub and bearing - no simple task.

EDIT: Of course it could be a case of "stiction" where the heads stick to the platters when spun down such that the platter motor doesn't have sufficient torque to overcome the mild 'adhesion' of the heads. Other than running the drive warm over a day or two, I'm not sure there is an easy fix for that.

 

[bretwashere]

I'm wondering if the flywheel can be removed to see what is accessible beneath. There may be a braking mechanism or a bearing accessible.

I'm leaning towards a bad bearing that MAY like a TINY drop of oil. These drives bearings were pretty noisy even 10 or more years ago. I just can't recall if the flywheel is easily removable. If you manage to get it off I'd suggest a light cleaning of the dust with a fine brush and vacuum cleaner suction to prevent any particle ingress into the bearing when a drop of oil is added.

I also can't recall if the flywheel is factory balanced. If you see what appear to be small indentations drilled out of the flywheel at various locations then that would be an indicator. In which case, you'd need to be able to re-align the flywheel with the motor shaft reasonably accurately upon re-assembly.


Otherwise I think you'd be looking at major surgery, removing head-pack, platters, flywheel, hub and bearing - no simple task.

EDIT: Of course it could be a case of "stiction" where the heads stick to the platters when spun down such that the platter motor doesn't have sufficient torque to overcome the mild 'adhesion' of the heads. Other than running the drive warm over a day or two, I'm not sure there is an easy fix for that.

This machine was an awesome find. After inspecting the contents on the hard drive, and from what the original owner told me, this machine was only used from 1989 to 1993. He bought a IIci and placed the Mac SE in its original box untouched since then. He stored it in his basement.

The hard drive, when functioning, sounds like any perfectly function stepper motor based hard drives from that time. The bearings are silent.

I do believe it is suffering from striction, as the computer sat in a box for 23 years untouched. I will try letting it run for a few days, plugged into a desktop's PSU molex connector. Thank you for all your help so far.