Data Head Alignment Check; Data Head Alignment; Description Of Circumferential Timing - HP 7925D Service Manual

7925
Table 3-1. Description of Circumferential Timing Conditions
Alignment and Adjustment
DATA GRAPH DESCRIPTION
Condition 1 Only one head is out of tolerance outside the lower limit. All the other heads are within
tolerance. (Refer to figure 3-9.)
Condition 2 Only one head is out of tolerance outside the upper limit. All the other heads are within
tolerance. (Refer to figure 3-10.)
Condition 3 Only one head is out of tolerance outside the upper limit. All the other heads are within
tolerance. (Refer to figure 3-11.)
Condition 4 Only one head is out of tolerance outside the lower limit. All the other heads are within
tolerance. (Refer to figure 3-12.)
Condition 5 Head 0 or heads 0 and 1 are out of tolerance outside the lower limit and head 7 or
heads 7 and 8 are out of tolerance outside the upper limit. (Refer to figure 3-13.)
Condition 6
Head 0 or heads 0 and 1 are out of tolerance outside the lower limit and head 7 or
heads 7 and 8 are out of tolerance outside the lower limit. (Refer to figure 3-14.)
Condition 7
All the heads are within tolerance, circumferential alignment is within the disc drive
specification. (Refer to figure 3-15.)
h. Check the clearance, shown in figure 3-17, between the
upper crash stop and the upper part of the carriage
assembly to ensure it is approximately 0.051 em (0.020
in.). If the clearance is not correct, perform steps i and j,
otherwise proceed to step k.
i. On the DSU, set the FUNCTION switch to position 7.
Note: Do not stop the spindle while the DSU is
set to FUNCTION 7. If the spindle must
be stopped, remove any tools from the
actuator assembly; set the DSU to
FUNCTION 1; press the START
pushbutton, then the STOP pushbutton;
and then set the RUN/STOP switch to
STOP.
j. Insert the head alignment tool into the servo head
alignment hole (see figure 3-5) with the "L-shaped"
handle end pointing upward. Adjust the head position
to obtain the clearance shown in figure 3-17. Rotate the
tool counterclockwise for more clearance, and clock-
wise for less clearance.
k. On the DSU, set the FUNCTION switch to position 7.
Note: Do not stop the spindle while the DSU is
set to FUNCTION 7. If the spindle must
be stopped, remove any tools from the
actuator assembly; set the DSU to
FUNCTION 1; press the START push-
button, then the STOP pushbutton; and
then set the RUN/STOP switch to STOP.
1.
On the DSU, press the START pushbutton. Ensure
that the head alignment meter pointer moves to the
far right, then to the far left, and then back again. If
the pointer does not perform as stated above, repeat
steps d through 1.
m. Ensure that the DSU is set to FUNCTION 7. Tighten
the servo head to 7.5 inch-pounds and repeat steps d
through 1 and then proceed to step n.
n. Perform the data head alignment check.
o. Perform the circumferential alignment check.
3-18. DATA HEAD ALIGNMENT CHECK. The
data head alignment check may be performed independent
of the alignment procedures to verify whether any or all
data heads are within tolerance. If any data head is out of
tolerance, perform the data head alignment procedure. To
check data head alignment, proceed as follows:
a. Perform the warmup procedure outlined in paragraph
3-13.
b. On the DSU, select the data head to be checked using
the binary combination of toggle switches H8 (C11),
H4, H2, and HI.
c. Set the FUNCTION switch to position 7, press the
START pushbutton, and wait for the completion of the
5-second cycle.
3-19