Card Cage Chassis And Motherboard Pca-A7; Power And Motor Regulator Pca-A9; Fault Indicator Pca-A12 - HP 7925D Service Manual

7925 Removal and Replacement
To replace the read/write preamplifier, proceed as follows:
a. Insert and firmly seat the PCA in the connector.
Loosen (do not remove) the two screws which hold
the preamplifier retainer (44, figure 6-4) and push the
retainer down. Tighten the two screws which hold
the preamplifier. Ensure that the preamplifier re-
tainer securely holds the read/write preamplifier.
a. Perform the preparation for service outlined in
paragraph 5-2.
b. Disconnect the ac power cord from the ac mains
power.
c. Open the front and rear doors and remove the front
shield (15, figure 6-1), the rear shield (13), and the
exhaust shield (11).
b. Connect the head connectors to the read/write
preamplifier. d. Rotate the three 1/4-turn fasteners that secure the
PCA to the bottom of the mainframe.
c. Install the preamp shield and secure with the three
mounting screws.
e. Lower the PCA into its service position.
d. Replace the shroud. (Refer to paragraph 5-3.) Restore
the ac power to the disc drive.
f. Loosen the air hose clamp (59, figure 6-2) screw and
disconnect air hose (60).
c. Remove the shroud. (Refer to paragraph 5-3),
To remove the card cage chassis (13, figure 6-2) and
motherboard PCA-A7 (16), proceed as follows:
a. Perform the preparation for service outlined in
paragraph 5-2.
b. Disconnect the ac power cord from the ac mains
power.
To avoid damage to the disc drive, en-
sure that the jumper on power and
motor regulator PCA-A9 is in the
proper position. (Refer to figure 4-26.)
g. Disconnect the four cables and the wiring harness.
To replace power and motor regulator PCA-A9, perform
the above steps in the reverse order.
h. Lift PCA straight up and out to disengage three
catches on edge of PCA from mating hinge hooks.
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CAUTION
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CARD CAGE CHASSIS AND
MOTHERBOARD PCA-A7
5-14.
d. Remove card cage PCA's. (Refer to paragraph 5-11.)
Note: Before removing the card cage chassis,
release the data cable from the cable re-
tainer at the rear of the card cage chassis
and release the fault indicator cable
from the cable retainer on the side of the
card cage chassis.
Note:
5-16.
Ensure the cables attached to PCA-A9
are pushed up into the groove (near the
hinges) in the mainframe before the
1/4-turn fasteners are secured to the
bottom of the mainframe.
FAULT INDICATOR PCA-AI2
e. At the bottom of the card cage, release the four
quick-release fasteners and lift out card cage chassis.
f. Remove read/write preamplifier PCA-A6. (Refer to
paragraph 5-13.)
g. On the motherboard, disconnect cabling, and remove
velocity transducer connector.
h. Loosen the screws (17) and lift out the motherboard.
Fault indicator PCA-AI2 is mounted on the back side of
the operator panel assembly. To remove fault indicator
PCA-AI2, proceed as follows:
a. Perform the preparation for service outlined in
paragraph 5-2.
b. Disconnect the ac power cord from the ac mains
power.
To replace the motherboard and card cage chassis, perform
the above steps in the reverse order.
c. Open the front door on the disc drive enclosure and
remove the front shield (15, figure 6-1).
To remove power and motor regulator PCA-A9 (49, figure
6-2), proceed as follows:
5-15.
POWER AND MOTOR
REGULATOR PCA-A9
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CAUTION
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To prevent connector damage, remove
the fault indicator ribbon cable from the
plastic clip located at the bottom of the
spindle logic card cage.
5-5