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AMSTRAD CTM644 - Disc Drive Alignment Procedures; Positioning Check and Adjustment; Index Timing Adjustment; Head Output Level Verification

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ALIGNMENT
CHECKS
(cant)
1)
Check
Positioning
1)
Load
CE Disk.
2)
Set
up
track
00,
Motor
off.
3)
Scope
to
TP5.
4)
Adjust
00
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
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
usee
±500
usee.
When
the
timing
is
not
within
this
range,
proceed
with
the
following
adjustment.
(Refer
to
Fig. 5-1).
6)
Loosen
the
tW'1
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
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
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
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.
15

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