formatting MFM drives on a IBM PC

Mike Stein mhs.stein at
Thu Sep 28 12:21:13 CDT 2017

----- Original Message ----- 
From: "Al Kossow via cctalk" <cctalk at>
To: <cctalk at>
Sent: Thursday, September 28, 2017 12:17 PM
Subject: Re: formatting MFM drives on a IBM PC

> On 9/28/17 7:38 AM, Mike Stein via cctalk wrote:
>> What is it that usually fails when the drive can't read the servo info? The data on the platter, or?
> I've never dug that far into it beyond fiddling with Micropolis trying to mechanically get it to
> find the servo tracks and calibrate to track 0.
> One of the problems is schematics and documentation on the servo systems are extremely difficult
> to get. The little that is on bitsavers is all I've come up with in 25 years of searching and there
> is practically nothing useful elsewhere on the web about fixing servos in old 5" disks.
> It could be heads, media, positioners, component aging in the analog section, etc etc..
Too bad. I'm probably not the only one who has drives that sound fine (i.e. no bad bearings, scratched surfaces etc.) but will not initialize; they twitch back and forth on startup, presumably looking for track 0, and then give up.

Seems like a shame to scrap them if only there were some remedy...


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