Sharp FDD-412A - Page 78

FDD412A/B
(2)
(3)
Magnetic head
~ Track #38
Fig. 4.24 Head Position (Tracking) Setting Requirements
Tools and measuring instruments to be used
(a) CE medium
(b) #2 Phillips screwdriver
(c) Synchroscope (1:1 probe x 3)
(d) Shorting-plug
(e) Tester or system
(i) Sides 0 and 1 should be switchable.
(ii) Seek should be available on tracks #0 to 38 to 76.
(iti) Head loading on/off operation should be possible.
(iv) DC power supply should be available.
Adjustment procedure
(a) Turn off DC power supply. Position the FDD vertically as
shown in Fig. 4.25.
(b) Turn the shaft at the step motor rear end to move the head
carriage toward the outermost track, until the step motor
pulley pin hits a stopper on the step motor keep plate.
(At this time, do not touch the head carriage, drive pulley
and steel belt.)
(c) Turn on DC power supply and insert the CE medium.
(d) Short-circuit JP2 at 4 and 6 with a shorting~plug to excite
phase 0 of the step motor.
(Steps (a) to (d) above are carried out to initialize the carriage
onto track 0.)
(e) Ste the synchroscope.
CH-1/2 : Observe the waveform at TP1 and 2 with the
differential mode. (V: 50mV/div., H: 10 ms/div.)
EXT TRG: Set to TPil. (INDEX-P)
(£) Load the head on and check that a head output waveshape
; appears.
If no waveshape appears, move the step motor a bit lightwise,
and hold it temporarily where a waveshape is output.
(g) Remove the shorting-plug installed in step (d) above.
(h) Seek track #38 and load the head on.
(i) Move the step motor a bit so that the head read output reaches
a maximum. (The output voltage is to be the peak value 20 ms
away form the index.) Note down this output voltages as
Vomax.
—~72—