AMSTRAD CPC6128 Service Manual page 15

ALIGNMENT CHECKS (cont)
1) Check Positioning
1) Load CE Disk.
2) Set up track OO, Motor off.
3) Scope to TPS.
4) Adjust OO Sensor (8 on Fig. 6) so that scope shows correct difference as Fig. 2.
2) Adjustment of Index Timing
1) Load the CE Disk (refer to disk info)
2) Step the disk to the track 39.
3) Synchronise the oscilloscope by TP9 (INDEX). Set the time base to 0.1msec/DIV.
4) Connect the probe to TP1.
Connect the ground probe to TP3 and TP11 (ground) of PCB.
Set the input to AC and set the vertical axis to 20mV/DIV.
5) Measure timing between sweep start and an initial data pulse. It should be 500 usec +500 usec.
When the timing is not within this range, proceed with the following adjustment. (Refer to Fig. 5-1).
6) Loosen the tw", screws fixed LED printed board. Adjust the position of LED printed board so that the
timing is 500 usec + 100 usec.
7) Re-check the timing.
8) Seek to the track OO and make sure that the timing is within 500 usec + 200 usec. Tighten the
screws. (Fig. 5 - 1).
3) Check of Head Output
This check is effective only when making write and read check as described below. If the outputlevelis
less than the prescribed output, clean the head before check.
Disk used for this check must be in good condition.
1) Load the CE Disk.
2) Select track 39.
3) Connect one of the probes of the oscilloscope to TP1 of the printed circuit board, another probe to
TP2, and the probe to ground to TP3, TP11 (ground).
Invert one channel, and set it to Add input, set input to AC, and set the vertical axis to 50mV/DIV and the
horizontal axis to 20msec/DIV.
4) Make sure tha average output level is the following value or more: 140 mV p-p (SN 25dB or more)
If the output is less than the above-described value, replace the head.
4) Adjustment of Positioning
1) Load CE disk.
2) Select Track 19.
3) Monitor the output in the same way as the head output inspection.
Calculate the off-track amount in reference to the calibration graph, showing the interrelation
between the burst amplitude ratio and off-track amount. (Refer to Fig. 5-2).
4) The average of amplitude ratio should be below 26 um.
If it is not within this range, make the following adjustment.
i) Loosen the bolt of the rotation stopper which fixes the screw shaft (Fig. 6-3).
Rotate the screw shaft and adjust it in such a way that the amplitude ratio may become below
15 uM. Tentatively set the bolt at that position.
ii) Make the to track step to the inner and outer circles and bring it to the original position. Make sure
that the adjustment is all right. Then, tighten the boi.
5) Confirmation of Head Azimuth
1) Load the CE Disk
2) Select Track 39.
3) Synchronise the probe of the oscilloscope by TP9 of PCB and connect another probe to TP1, and
the probe ground to TP3, TP11 (ground). Set the input to AC, the vertical axis to 10 mV/DIV, and the
horizontal axis to 0.5 msec/DIV. Make sure that the two outside burst waveforms are smaller than
two inside burst waveforms as shown in Fig. 5-3.
Note: Signal preceding the azimuth burst is the index burst.
If the azimuth is still incorrect reeplace the head assembly.
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