HP 7925D Service Manual page 135

7925
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CAUTION
I
The read/write preamplifier PCA-A6
contains a CMOS component. To avoid
damage to the CMOS component, do not
touch the components or the circuit
traces on the PCA.
g. Disconnect head cable connector to be removed from
read/write preamplifier PCA-A6.
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CAUTION
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To avoid damage to the head, be sure to
install the head installation tool on the
head as shown in figure 5-2.
h. Install the head installation tool as shown in figure
5-2. The UP side of the installation tool is used for
heads 1, 3, 4, 6, and 8. The DN side of the installation
tool is used for heads 0,2,5, 7, and the servo.
i. Hold the head in place by applying a slight pressure to
the head installation tool, then loosen the head secur-
ing screw.
j. Remove the head with the head installation tool at-
tached. Care must be exercised to avoid damaging
critical alignments of the head assembly.
To replace a data or servo head, proceed as follows:
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CAUTION
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To avoid damage to the head, do not
touch or clean the surface of the head
that attaches to the actuator.
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CAUTION
I
To avoid damage to the head, be sure to
install the head installation tool on the
head as shown in figure 5-2.
a. Install the head installation tool as shown in figure
5-2. The UP side of the installation tool is used for
heads 1, 3, 4, 6, and 8. The DN side of the installation
tool is used for heads 0, 2, 5, 7, and the servo.
b. Clean the head surface as outlined in paragraph 2-15.
c. Before seating the head in place, pull head cable
through slot into which the head positions.
d. Replace head and thread in head securing screw.
e. Using fingers, thread in screw until it isjust snug and
the head remains in place.
Removal and Replacement
I"
A I I T l n .. 1
"',,",u
I I V I , .
Do not tighten head securing screw with
head installation tool attached to head,
as the heads will not seat properly in
the carriage. Damage to the head and
disc surface is likely to occur if the head
is tightened with the tool in place.
f. Remove the head installation tool. Ensure the re-
placement head is properly positioned on the head
cam (see figure 5-3).
g. Insert the head initial position tool to ensure the head
alignment screw can be adjusted through the head
alignment hole in the coil/carriage assembly.
h. Tighten the head securing screw to 5 inch-pounds,
and remove the head initial position tool.
i. Replace the card cage, card cage PCA's, pack chamber
assembly, and the front frame assembly.
j. Reconnect all cabling disconnected prior to head
removal. If applicable, replace the contamination
shield (25, figure 6-2).
k. Perform the head alignment procedures given in Sec-
tion III, Alignment and Adjustment. Measure the air
pressure of the absolute filter as outlined in
paragraph 2-13.
5-19. CARRIAGE LATCH AND
DETECTOR ASSEMBLV
REMOVAL AND REPLACEMENT
To remove and replace the carriage latch and detector
assembly (5
an~
7, figure 6-7), proceed as follows:
a. Perform the preparation for service outlined in
paragraph 5-2.
b. Disconnect the ac power cord from the ac mams
power.
c. Remove the shroud. (Refer to paragraph 5-3.)
d. Remove the card cage PCA's and card cage chassis.
(Refer to paragraphs 5-11 and 5-14.)
e. Disconnect the connector from the detector (5) and the
two connectors from the carriage latch (7).
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CAUTION
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Exercise care when handling the ac-
tuator assembly if the carriage latch and
detector assembly is removed. Carriage
movement is no longer restrained and
damage to the heads may result.
5-7