50-pin SCSI HDD won't mount

[JDW]

I've got an Apple-branded Quantum Fireball 1280S 1.2GB 3.5" SCSI drive that won't mount. If I change the SCSI ID via jumpers, SCSI Probe shows the correct ID every time. But SCSI Probe won't mount it, nor will any other Utility app I've tried. Most utility apps (Lido, SilverLining, etc.) simply throw an error when they reach the drive's SCSI ID. Other apps like Apple's Disk First Aid don't see the drive at all.

The drive spins up, and I can hear what sounds like some initial head movement, but again, the drive won't mount. The drive has a TE (Terminal Enable) jumper, but despite having that set (termination enabled), it still won't mount. I've been testing it with my SE/30 booted into System 7.1 and OS8.1 (via ROM-inator II Mega).

Any thoughts on what might be preventing it from mounting?

This is a drive someone mailed to me in hopes of having me extract data from it.

 

[Paolo B]

Quantum Prodrive ELS, 160 Mb, 1992. Apple ROM, originally installed in a Color Classic.

When powered up, it spins, but after a few secs it spins down and that’s it.

Now, I managed to fix a couple of PowerBook internal drives with similar issues.
For those drives the root cause was the stuck head: the parking bumper got sticky due to deterioration of the rubbery material, so the head remained literally glued. With the aid of some tape, issue was somehow addressed and the drives still work today when sporadically used.

So, on to this unit.

Lid removed, diagnosis confirmed: stuck head.

I applied on the cantilever side the necessary force for releasing the head (which felt definitely stuck) and then the drive got back to life. However, it just lasted the time for running some diagnostic tests (everything fine, no bad blocks or stuff), but then the situation repeated.
Head remains stuck, but now it doesn’t feel “glued”, just unable to move. You can see it wiggling about the parking position, but it doesn’t travel. Seems like it gets parked too far, “out of range”.

Now, I don’t want even to consider disassembly the disk or what. It’s impossible to put it back together, for me it’s a dead drive…

…until I came into this:

Quantum ProDrive ELS Repair Insert - Fix your classic Macintosh hard drive!

Quantum ProDrive ELS Repair Insert - Fix your classic Macintosh hard drive! | eBay

This ABS plastic insert corrects the stuck head problem common on Quantum hard drives used in old Macintosh computers from the 80's and 90's. Take care to keep the disk's platter covered. Seat the left side of the insert into place.

www.ebay.com

Seems like a wedge that is preventing the head from moving to the parking position.

Does anyone have experience with this stuff?

(Anyhow, in between leaking caps, faulty floppy drives and failing hard drives, it must be reckoned that early nineties products’ quality was questionable, to say the least)

 

[Paolo B]

I confirm it should be possible to glue a calibrated wedge stopping the cantilever and the head from being parked ”too far”, without interfering with the break.
Not easy to fabricate and install one, though, as the margin is very tight.

 

[Paolo B]

Eventually, I built shims by overlapping layers of thick aluminum tape. The idea is to pack enough layers to prevent the head to be parked too far, but not enough for preventing the brake to engage.
The drive is now fully functional again. Surely, I wouldn’t store the keys to a cryptocurrency portfolio, but for playing SimCity will be more than OK.

 

[YMK]

Seems like a wedge that is preventing the head from moving to the parking position.

Does anyone have experience with this stuff?

I do, because I make them and they do work.

The head can still park, but it can't contact the bumper.