6300
6.14.6 CIRCUMFERENTIAL ALIGNMENT - FRONT LOAD
(2200
BPI)
6.14.6.1
Test Procedure
(100
and
200
tpi)
(1)
Set oscilloscope
as
follows.
• Connect oscilloscope Channel 1 vertical input
to
TP19
on the Read/Write
PCBA.
• Connect oscilloscope Channel 1 ground
to
TP18
on the ReadlWrite PCBA.
• Set Channel 1 vertical sensitivity
to
0.1
v per division .
• Connect oscilloscope Channel 2
X1
0 probe to
TP2
on the Logic PCBA.
• Set Channel 2 vertical sensitivity to 0.2v per division.
• Set Channel Select to Alternate mode.
• Use internal sync and negative sync on the leading edge
of
index signal on
Channel
2.
• Set the sweep rate
to
5
JJ.sec.
NOTE
Depending on the type
of
oscilloscope utilized and its
grounding arrangement,
it
may
be
necessary
to
use a
differential measurement
of
the Read/Write
PCBA
signal in
lieu
of
a single channel method. This
will
usually
be
the
case when
a ground loop exists between the scope and the
disk drive. Refer to the applicable oscilloscope manual for
differential measurement set-up,
if
necessary.
• Adjust horizontal position to place start of sweep on left-most vertical graticule
line. This will establish a time-zero reference to
be
used
in
lieu of actual viewing
of the negative transition
of
the index pulse.
Take care not to disturb the horizontal position during the measurement. (This
technique assumes that the start
of
the sweep corresponds
to
the triggering of
the sweep.
Verify
this
if in doubt.)
(2)
Set exerciser
to
position heads to cylinder
095
(190
for
200
tpi).
(3)
Select head
O.
(4)
Observe the waveform at
TP19
with respect
to
the falling edge of the Index signal
(time-zero reference).
(5)
The first pulse of the waveform at
TP19
should occur
30
% 5
J.lsec
from the
negative-going edge of the
Index signal (time-zero reference).
See
Figure
6·28.
(6) Select head 1 .
(7) Observe the waveform at TP19. The first pulse should occur
30
± 5
J.lsec
from the
negative-going edge
of
the Index Signal (time-zero reference).
(8)
Alternately switch between heads 0 and 1, and observe the relative displacement
of the pulse for each head. The total displacement (separation) between pulse
pOSitions must
be
10
JJ.sec
or less.
See
Figure 6·29.
6-60
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