Interesting drive failure

[Tom Gardner]

On 4/22/15 5:04 PM, David Gesswein wrote:

> Head alignment off on those heads. Can the drive microstep or any 
> other way to change the head alignement? You might be able to recover 
> the data that way.

Some SMD drives could microstep and some controllers implemented it.  Not
sure about yr drive or its controller.  BTW, I did several searches for info
on the Fujitsu drive without any luck.

If u can get a utility to loop on reading a specific track and head then you
can apply finger pressure to the top of the carriage to force the head
slightly off track in either direction to see if it reads better in one
direction or the other.  Be careful with both pressure and location because
if the servo decides it's lost it will probably do a recalibration which
happens quickly and with force - could damage the finger.

With an oscilloscope u can observe the raw head signal (differentially) and
see if it increases in one direction or another.  U can probably read single
ended if u can figure out where is the output of the read preamplifier
(might even be right next to the head stack).

With a schematic, power supply and variable resistor u can inject an offset
signal into the servo loop and move the heads off tract to the maximum head
amplitude position.  Again start low and slowly increase the injected
signal.

Tom