AMSTRAD PC1640 - Index Burst Time Adjustment; Lever Check

5-5
Index
Burst Time
Adjustment
a)
Insert
and clamp a CE
diskette.
b)
Move the
head to
track 34 and
check the
index
burst time
of the top
and
bottom heads.
Adjust
if the
timing
of
one of
the
top
or
bottom head
is not as
shown in
Fig.
5-5.
c)
Move the index
sensor
assembly
back or
forward by
slightly
loosening
the
index
sensor
assembly
fixing
screw to
adjust
the index
burst
time, then
secure
with the
screw.
d)
Check
the index
burst time of
the top
and bottom
heads.
e)
Repeat
from (c) if
adjustment
fails.
Index
Measuring
condition
Channel
1 -TP1
(10mv/div)
Channel
2 -TP2
(10mv/div),
invert
Mode
-ADD
Sweep
-100 us/div
Trigger -Edge
connector J2
-
8,
slope
Ifew
Reading
Output Signal
Screw
I
ndex Sensor
'
/ui®iuBl-H
i-jr
®
ufD
he
T
=
200
±
200
/is
qA
Fig.
5-5
Index Burst Time
Adjustment
5-6
Lever
Check
a)
Insert
and
clamp
a
blank diskette.
b)
Move
the heads to
track 39 and
write 2F by
the top
and
bottom heads.
c)
Check
that
the average
output
levels of the top
and
bottom head
is
more than
270mV.
Perform
the
following if
the
output
level is
below the
required
standard.
d)
Insert
another
blank diskette
and
reconfirm.
e)
Check the
spindle
speed as
described
in
5-1.
f)
Change
the
oscilloscope mode to
the CHOP
mode
and
check the TP1
andTP2
outputs.
Exchange
the
printed
circuit
board of
one output
is smaller
than
another one
or missing,
even
though
the probes
are
normal.
g)
Exchange
the head
assembly if
no problems
are
encountered
in (d), (e).
Measuring
condition
Channel 1 -TP1
(10mv/div)
Channel
2 -TP2
(10mv/div), invert
Mode
-ADD
Sweep
-20ms/div
Trigger -TP6
Head Reading Output Signal
(TP1-TP2;
A
=
270mV
min.
Fig.
5-6
Level Check
13