Shugart SA455 - 5.4.5 Index;Sector Timing Adjustment

5.4.5 Indexl Sector Timing AdJu8tme!nt
a. Insert alignment diskette SA128 or SA126.
b. Start motor
and select heald O.
c. Step carriage to track 01 (SA455) or track 02 (SA465).
d. Sync oscilloscope external positive
on TP7 (+ Index). Set time base to 50 J,tsec/dlvlsion.
e. Connect one probe to TPl and other to TP2. Ground probes to PCB. Set Inputs to aCt ADD.
and invert one channel. Set vertical deflection to 500 mV/dlvlslon.
f. Observe timing between start of sweep and first data pulse. This should be 200 + 200/ -100
J,tsec. If timing Is not within tc)lerance, continue on with adjustment. See figure 5·10.
g. Loosen mounting screw In Index detector block until assembly Is just able to be moved. See
figure 5·11.
h. Step carriage to track 38 (SA455) or track 76 (SA465).
i. Observing timing, adjust detector until timing Is 200 + 200/ -100 J,tsec. Ensure that detector
assembly
is against registrcltlol"\ surface on hub fl:ame.
j. Tighten mounting screw.
k. $tep carriage to track 01 (SA455) or track 02 (SA465).
I. Recheck timing.
m. Repeat for head 1.
50 mV 50 Jtsec
..... -+--'t- _-..-I~I __ +--I--t INDEX BURST
~ ~ I I I 200/tsec ± 100/tsec
..... _--,--_ .... __ .._ .. _-----
50 mV
IFIGURE 5·10. INDEX BURST
5·12
39239·13