Sharp FDD-412A - Page 80

FDD412A/B
&. 3.2
(1)
(2)
(3)
Q Track Sensor Position Adjustment
Objective and setting requirements
When the carriage returns to track #0, the TRACK 00 signal should
be properly sensed.
Tools and measuring instruments to be used
(a) Work medium
(b) #2 Phillips screwdriver
(c) Synchroscope (1:1 probe * 2)
(d) Shorting-plug
(e) Tester or system
(i) Seek should be repeatedly possihle on tracks #0 to 4
to 0.
(ii) DC power supply should be available.
(£) IC clips (standard 14-pin type x2,-‘or 28-pin type x1)
Adjustment
(a) Turn off DC power supply.
(b) Turn the shaft at the step motor rear end to move the head
carriage towrad the outermost track, until the step motor
pulley pin hits the 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 and insert the work medium.
(d) Short-circuit JP2 at 4 and 6 with a shorting-plug to excite
phase O of the step motor.
(Steps (a) to (d) above are carried out to initailize the carriage
onto track #0.)
(e) Set the synchroscope.
CH-1: TRACK OO-P (IC14-12 pin or 1C12-22 pin)
CH-2: STEP-N (1C5-11 pin or 1C12-7 pin)
(f) Remove the shorting-plug installed in step (d) above.
(g) Loosen the set screw on the 0 track sensor, and move the
sensor toward the outermost track (i.e., away from the
spindle).
(h) Move the 0 track sensor bit by bit toward track #76, and
hold it temporarily where the TRACK 00 signal is brought
"High" for the first time.
(i) Repeat seek operation on track #0 to 4 to 0, and fine-
adjust the sensor position so that the TRACK O0-P signal
and
STEP
signal
appear
in
such
a
relation
to
each
other
as
shown in Fig. 4.26. This adjustment is made easier by
following the steps given below:
(i)
Set
the
range
of
the
synchroscope
to
2V/div.,
2
ms/div.
(ii) Get a correct synchronization with the STEP-N signal
at CH-2.
(iii)
Turn
the
time
axis
rheostat
to
adjust
the
time
axis
so
that
the
waveshape
shown
in
Fig.
4.27
appears.
a 7