Use Of Circumferential Timing Tolerance Label - HP 7925D Service Manual

Alignment and Adjustment 7925
DSU FUNCTION
POSITION
POSITION 4
POSITION 5
POSITION 6
* For proper test values
refer to the CE disc
pack dust cover.
7311-73
H8 0 0
0 0
0
0
0 0 1
H4
0
0 0 0 1
1 1 1 0
H2
0
0 1 1 0 0 1
1
0
H1
0
1 0
1
0
1 0 1
0
DSU
POSITIONS
0- Switch set to LEFT
SWITCH
1 - Switch set to RIGHT
DSU TOGGLE SWITCH POSITIONS
Figure
3-7.
Use of Circumferential Timing Tolerance Label
a. Perform the warmup procedure. (Refer to paragraph
3-13.)
Perform the data head alignment check. (Refer to
paragraph 3-18.)
b. On the DSU, set the FUNCTION switch to position 4
(Cyl 0).
c. Select a head using the binary combination of toggle
switches H8, H4, H2, and HI on the DSU.
d. On the DSU, press the START pushbutton and note
the time on the digital display. Referring to the cir-
cumferential timing tolerance label on the CE disc
pack, look in the row labeled Cyl 0 and in the column
for the head selected. The digital display reading on
the DSU should be greater than or equal to the first
number and less than or equal to the last number in
the column.
e. On the DSU, set the FUNCTION switch to position 5
(Cyl 410).
f.
On the DSU, press the START pushbutton and note
the time on the digital display. Referring to the cir-
cumferential timing tolerance label on the CE disc
pack, look in the row labeled Cyl 410 and in the
column for the head selected. The digital display read-
ing on the DSU should be greater than or equal to the
first number and less than or equal to the last number
in the column.
g. On the DSU, set the FUNCTION switch to position 6
(Cy1820).
h. On the DSU, press the START pushbutton and note
3-8
the time on the digital display. Referring to the cir-
cumferential timing tolerance label on the CE disc
pack, look in the row labeled Cyl 820 and in the
column for the head selected. The digital display read-
ing on the DSU should be greater than or equal to the
first number and less than or equal to the last number
in the column.
i. Repeat steps b through h for each data head.
j.
If all the heads are within tolerance, the circumferen-
tial alignment is correct.
k.
If any or all heads are
not
within tolerance, refer to
paragraph 3-15.
1. On
t.he rlis~ rlrivp.; sP.t thp. RUN/STOP switch to STOP.
m. Remove the CE disc pack from the disc drive.
n. On the disc drive, set the READ ONLY switch to the
unprotected position.
o. Remove the DSU and the head alignment PCA from
the disc drive and then replace all cables removed
during the DSU installation.
p. Replace the shroud on the disc drive enclosure.
3-15. CIRCUMFERENTIAL ALIGNMENT. This
procedure is used to correct the circumferential alignment
of the disc drive. To properly perform this procedure, the
following conditions must be met:
• Use a DSU that has a date code of 1845 or greater.
The date code is located on a tag on the back of the
DSU.