Interesting drive failure...

[Josh Dersch]

On 4/22/15 5:04 PM, David Gesswein wrote:
> On Tue, Apr 21, 2015 at 10:54:42PM -0700, Josh Dersch wrote:
>> So, I suppose this is somewhat good news in that I may be able to
>> use the drive, but I wonder what would cause the data on the disk to
>> fail in such a manner (and I'm still hesitant to reformat the drive
>> without recovering stuff off of surfaces 2/3...)  Any thoughts?
>>
> Head alignment off on those heads.
That makes sense.


>   Can the drive microstep or any other
> way to change the head alignement? You might be able to recover the
> data that way.
According to the service manual one of the surfaces contains servo 
tracks used to position the heads, and all alignment is based on these 
tracks.  If some of the heads are now out of alignment with those tracks 
I don't think there's anything to be done about it (but I've only 
skimmed the manual thus far).  There does not appear to be anything I 
can do at the interface level, at any rate.  I wonder, though, if 
perhaps running the drive in a different orientation (it's currently on 
its side) might have an effect on the wayward heads.  Probably not, but 
it's worth a shot.  I may try that tomorrow...

>
> I have seen an MFM drive with a few heads so out of alighment that
> you got data from track n+1 on one head and n on another. Not sure
> how you cause that without more serious damage to the drive.
Yeah, I know nothing of the history of this machine, it seems to have 
been well treated aside from being left in a somewhat damp and 
rat-infested environment, no evidence of it being dropped.  But then, 
the chassis on the Ridge is built like a tank so it might very well have 
been dropped a few feet to no obvious effect...

> For MFM
> drives orientation or finger on the stepper motor helps to recover
> data when the heads are off. Probably doesn't work with your drive.
>
Yeah, there's no stepper to grab onto here.  And if there was, it'd 
probably take my finger off when it moved, this drive means business :).

Thanks,
Josh