AMSTRAD CPC664 - Page 15

ALIGNMENT
CHECKS
(cont)
1)
Check Positioning
1)
Load
CE Disk.
2)
Set up track
OO,
Motor
off.
3)
Scope
to
TP5.
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
0.1 msec/DIV.
4)
Connect
the probe to TP1.
Connect the ground probe
to
TP3 and TP1 1 (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 usee ±500 usee.
When the timing is not within this range, proceed with the following adjustment. (Refer
to
Fig.
5-1
).
6)
Loosen the two screws fixed LED printed board. Adjust the position of LED printed board
so
that the
timing is 500 usee ±100 usee.
7)
Re-check the timing.
8)
Seek to the track
00
and make sure that the timing is within
500
usee ± 200
usee.
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 output level is
less than the prescribed
output,
clean the head before check.
Disk used for this check must be in
good
condition.
1)
Load
theCE
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, TP1
1
(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: 1
40
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 urn.
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 bolt.
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
toTP1
,
and
the probe ground
to
TP3, TP1 1 (ground).
Set
the input to AC,
the vertical
axis
to
1 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.
15