View Full Version : MFM Drive Mechanical Repair

December 15th, 2016, 01:33 AM

I'm currently in the process of repairing and restoring an IBM 5160 XT, manufactured here in Australia at IBM's former Wangaratta, VIC plant. It seems like whenever I search for information, Google directs me here, so I figured it was about time I created an account.

(If anyone wants to see the current progress of said XT, I've created an album here. (http://imgur.com/a/gR3JW))

Recently I've started messing around with MFM drives, four to be exact:

MiniScribe 8425 (20MB)
Seagate ST-412 (10MB)
Seagate ST-213 (10MB)
Seagate ST-251 (20MB)

The MiniScribe works perfectly, and the Seagate ST-412 is serviceable with no bad sectors, but it's noisy. The ST-213 remains unknown as I don't have a usable controller, and the ST-251 has visible platter damage.

Of these four, the ST-412 is the one I'm most determined to salvage. I'm convinced it needs new bearings, which would be incredibly difficult I'm aware, but I never one to shy away from a mechanical repair challenge. The IBM XT chassis was already a metal and paintwork job in itself, so I've accepted that no repair to this machine will be easy. Also yes, I have already used some lithium grease around the channel surrounding the motor.

Most standard bearings can be sourced relatively easily, in deep-groove, sealed, shielded, tolerant of axial loads, and so forth so those aren't a problem. The question I suppose is whether Seagate used a standard roller or ball bearing assembly to support the spindle shaft, and if so, where within the drive mechanism it was used. Was it a press-fit into the drive casting, or integrated deep within the electric motor assembly?

I know it's a long shot but if someone had more detailed knowledge of the ST-412, or even some photos of a dead or disassembled drive, it would be a great starting point.

Otherwise the MiniScribe 8425 is certainly usable, and with a compatible controller, the ST-213 could be as well. I've also explored adding an XT-IDE, but even so this is a restoration job, so any newer connection interfaces should ideally complement the factory storage. Wouldn't want to lose that trademark MFM drive sound.