Advertisement
ALIGNMENT
(Continued)
If
the
125kHz
signal
Is
not present,
step
the
AZIMUTH CHECK
head
forward
or
back
until
the
125kHz signal
Is
present.
When
the
125kHz
signal
Is
present
on the scope, the head
Is
on Track 00.
Connect
the
Input
of
a
voltmeter
to
TP3.
Check
for
5V
when the Head
Is
on Track 00
and
0V
when
the
Head
Is
on
Track
02.
If
the
readings
are
not
correct,
set
the
Head
to
Track
01,
loosen
the
Track
00
Sensor
(M2)
screw(see
Disk
Drive Mechanical
Photo)on
the
top of
the Disk
Drive and adjust
the
detector
until
the
voltmeter
reading
jumps
fr^m 0V
to
5V.
Tighten
the
Track
00
screw
and
recheck
the Track
00 Sensor adjustment.
INDEX
SENSOR ADJUSTMENT
Connect
the
channel
A
Input of
a
dual
trace
scope
to
TP8,
channel
B
Input
to
TP1
(
Index
pulse)and
the
scope
ground
to
TP6.
Set the
scope
display
to
channel
A
with
the
voltage
range
set
to
20mV
and the sweep time
set
-ho
50uS.
Set
the
channel B
Input
to
nonlnvertlng
mode
and trigger the scope
on
channel B wtth
the
trigger set to negative slope.
Insert
the
Alignment
Dtskette
In
the
Disk
Drive and close
the door.
Turn
On
Disk Drive,
select side
and
set the
head
to
track 01.
Confirm
that
the
leading
edge
of
the
burst
occurs 200uS ±200us after
the
leading edge
of
the
Index
pulse,
see
Figure
3.
If
the
Index
Sensor
(PQ51)
Is
out
of
adjustment,
loosen
two
screws
holding
the
board
with
the
Index
detector
on
the
top
of
the
Disk
Drive
and
adjust
the
Board
for
200ust200us,see
Disk
Drive Mechanical,
Top View
Photo.
If
side
checks
good,
select
side
1
and
repeat
the
above procedure to check Head
1.
Figure
3
Connect
the
channel
A
Input of
a
dual
trace
scope to TP7,
channel
B
Input to TP8,
external
trigger
Input
to
TP1
and
connect
the
scope
ground
to
TP6.
Set
the scope
to
add mode with
channel B
Inverted,
sweep time to .5ms, AC In-
put,
trigger
to
negative slope and voltage
to
.1V
range.
Insert
the
Alignment
Dtskette,
turn
on
the
Disk Drtve,
select side
and set
the head to
track
34.
Confirm that
the pattern appears as
shown
In
Figure
4.
The amplitude
of
bursts
1
and
4
must
be
equal
to
or
less
than
the
amplitudes
of
bursts
2
and
3.
If
the
azimuth
of
Head
checks
good,
select
side
1
and repeat
the above procedure
to
check
the
azimuth
of
Head
1.
Figure
4
READ CIRCUIT ADJUSTMENT
To
do
this adjustment
a
Disk Drive Tester or
program
Is
required
that
will
continuously
write
a
1F
<62.5KHz)
pattern
on
a
blank
dtskette Inserted
In
the Drtve.
Connect
the
Input
of
a
scope to pin
3 of
IC
U4
(Read
Data
Line).
Set
the
sweep
time
to
2u
Sec,
voltage
range
to
2V
and
trigger
on
negative
slope.
Insert
a
BLANK
dtskette
In
the
Drive
and
close
the
Drive
door.
Continuously
write
a
IF
pattern
to
the
diskette.
Two
pulses
should
appear
on
the
scope
screen.
If
the
Phase AdJ Control
(R1)
Is
out
of
adjustment,
the
second
pulse
will
appear
to
be
two
pulses
out
of
phase,
see
Figure
5.
If
R1
Is
out
of
adjustment,
adjust
It
until
the
second
pulse
appears
to
be
one
pulse, see
Figure
6.
2
pulses
2
o
S-
1
o <
o
w
X
Figure
6
11
Advertisement
