prolly a failing ic of some sort?
On Thu, Sep 28, 2017 at 11:21 AM, Geoffrey Oltmans via cctalk < cctalk@classiccmp.org> wrote: > On Thu, Sep 28, 2017 at 11:17 AM, Al Kossow via cctalk < > cctalk@classiccmp.org> wrote: > > > > > > > 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.. > > > > > > > > > > Speaking of.... I've got a couple of old MFM drives (10 and 20 MB of a > variety whose name and model #'s escape me, I wanna say Tandon, but not > sure). They seem to work fine when I initially format and partition, but as > they run for a while, they get more and more unreliable. It seems to be a > function of how long they've been running for rather than a predictable > pattern of bad tracks sectors? Are there any good sources of > troubleshooting info at the controller level for these old drives? >
