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Fujitsu M255XK Customer Engineering Manual page 54

5 1/4" mini-flexible disk drive
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4.4.12 Index Burst Timing Inspection and Adjustment
Tools Required:
Phillips Screwdriver, M3
Alignment Disk
Exerciser (AVA 409 or equivalent)
Oscilloscope
Screw Lock Liquid
Intraconnector . 34-pi n
Refer to Figure 4-14.
1.
Set the oscilloscope as follows:
Channell: Connect to TP1 (pre-amp), AC mode, 0.2V per division.
Channel 2: Connect to TP2 (pre-amp), AC mode, 0.2V per division.
Time Base: Set to 50 microseconds per division.
Trigger:
Connect to pin 8 or intraconnector (Index), DC mode.
Set Trigger mode to External, on the negative edge (this will start the
sweep at the beginning of each disk rotation).
2.
Start the Spindle Motor and load the alignment disk.
3.
Seek the Read/Write heads to Track 02.
4.
Measure the duration of "t" in Figure 4-14.
INDEX
Pre-amp
+---\1
t
Index bu.rst delay
Figure 4-14 Index Burst Timing
5.
Ensure that Index Burst Timing is within the range of 200
±.
150 microseconds,
for all models in the M255XK family. Switch heads and reverify timing.
6.
Seek the read/write heads to track 68.
Verify the Index Burst timing is still
within specifications. Switch heads and reverify timing.
7.
If
the timing at either track 2 or track 68, head 0 or head 1, is outside of
speci fications, proceed to step 8 and adjust the Index Sensor to achieve a
balance point between the four locations (tracks 2 and 68, heads 0 and 1).
TS-021-013087 ••• 01
4-22

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