Index Burst Time Adjustment; Level Check - AMSTRAD PC1512 Service Manual

5-5
Index Burst
Time Adjustment
a)
Insert a
CE
diskette.
b)
Move
the
head
to
Track
34 and check
the index burst times
of
top
and bottom heads. Adjust as
follows
if
the timing
of
one
of
the top or
bottom heads
is
not
as
shown
in
Figure 5-3.
c)
Move
the index sensor
assembly back and
forth
by slightly
loosening the index sensor assembly
fix
screws
to
adjust the
index burst time.
d)
Check the index burst
times
of
the top
and bottom heads.
e)
Repeat from
c)
if
adjustment has
been
unsuccessful.
Measuring Conditions
Channel
1-TP1 (10mV/div)
MODE-ADD
Channel 2-TP2 (10mV/div)
Sweep-0.1 ms/div
Trigger-
Edge Connector J2
8 pin.
Slope
( ••)
I
N D
Hea
d
Reading Output
Si
(
T P
I
-
T ? 1
)
!00:£00jj
s
270mV.
5-6 Level
Check
a)
Insert
a blank
diskette.
b)
Move
the
head
to
Track
39 and
write
2F
by the top
and bottom
heads.
c)
Check
that
the
average output
level of
the top
and bottom heads
is
more
than
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
to
the
CHOP
mode and check
the
TP1 and TP2
outputs.
Exchange
the
printed
circuit
board
if
one output
is
small
or missing,
even
if
the
probes are normal.
g)
Exchange
the
head assembly
if
no problems
are
encountered
in
d), e).
and
f)
above.
Measuring Conditions
Channel 1-TP1 (10mV/div)
MODE-ADD
Channel 2-TP2
(10mV/div)
Sweep-20ms/div
Trigger—
TP6
Head Reading Out
Signal
(TP1-TP2)
^%>wi&P*
^*=*hmji^
A
A = 270 mV
I"
i
n
13