Head alignment for legacy Sony FDD

Peter pludikar at sympatico.ca
Mon Jan 21 19:47:21 CST 2008

> 4 shorted together ('measuer 0') and one unconencted one would be what I 
> expect.

> The uncconected one will be at one end of the head edge connector 
> fingers. On the damaged head, which _other_ one is unconnected ?

On the damaged head, three fingers at one end show shorted.  I guess that
means: 3) Other end of the R/W coil, 4) Centre tap of R/W and 5) Erase
Are probably okay. Finger 2) shows o/c  - this would be consistent with the
fact that before I managed to fry the drive, the FDD could read data but on
writing I lost all data (ie everything was erased) 

>> there's a variable pot RV101 and 2 pins to IC101
>> (CXD1007B) associated with X-adj and X-reset

> Are these related to head alignment? I must say I am rather suprised. 
> Normally you physically move the head stepper motor slightly.

There doesn't appear to be a physical way of moving the heads - I was
speculating/hoping that RV101 and the 2 X related pins may have something to
do with fine adjustment - but I have no real idea.  The heads are mounted on
a diecast bracket with locating holes.  There are corresponding centring
pins on the main diecast body and there's no discernable movement when the
two are mated.

I rigged up a small Shugart type interface board with manual switches that
allowed me to exercise the main drive control (drive select, motor on, step
direction, step etc.). The control logic on the FDD stops the head from
stepping in the down direction once the track 0 sensor is activated.  So my
one of my thoughts is that the track 0 sensor actually defines the fine head
position, but I don't know for sure.  Any thoughts or suggestions?


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