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View Full Version : Osborne 1A back to life!



Brendan
May 28th, 2011, 07:13 PM
I had recently picked up an Osborne 1A in pretty good shape from the local Austin, Texas, Goodwill Computer Works for $40.

After fumbling about trying to image disks in my very limited spare time (I don't have a dedicated DOS box for imaging single density floppies, although have been successful with DD under Linux) I picked up some Osborne 1A CP/M disks from eBay.

These proved to be unreliable. It seemed like they might boot once or twice and then not work until the system was shut down and sat for awhile. At the eBay seller's suggestion, I gave in today and opened up the case, pulled out the floppy drives and discovered that the spindle motors simply weren't spinning at the right rate (using the 60Hz strobe markings) on either drive. After adjusting the trim-pots, the system is working great and I was able to boot, use, and backup all the floppies.

To most of you hackers, this probably seems like part of an ordinary day, but for me, it was a small victory. :D

On another note, this is the first time I recall seeing drives that used a stepper motor driving a worm gear to position the head. Is this common, and I just never noticed it before? These drives carry a Siemens sticker.

tezza
May 29th, 2011, 02:36 AM
Well done! An easy fix. It was good you had a crack at it.

Yes, I've seen that worm gear arrangment in a few 5.25 inch full height drives.

Tez

glitch
May 29th, 2011, 04:42 AM
On another note, this is the first time I recall seeing drives that used a stepper motor driving a worm gear to position the head. Is this common, and I just never noticed it before? These drives carry a Siemens sticker.

Yep, this is pretty common. I believe all of my 8" drives use worm gears, and many of my FH 5.25" drives do. Actually, I think most 3.5" drives use a worm gear too! Make sure you keep it cleaned and lubricated -- just about every 8" drive I've used had the old worm gear grease turn solid, and needed to be dissolved with WD-40 and re-greased (I use white lithium grease)

Brendan
May 29th, 2011, 10:29 AM
Very interesting - this must be my general lack of experience with full-height drives. I keep lithium grease on hand (good for squeaky car doors) so that will work out nicely. Thanks for the info, guys.