Velocity Transducer And Velocity Transducer Shaft - HP 7925D Service Manual

Removal and Replacement
Article Coordinator at
Hewlett-Packard Disc Mem-
ory Division by phoning
(208) 376-6000.
To remove the actuator assembly, 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.
c. Remove the shroud. (Refer to paragraph 5-3,)
d. Remove card cage PCA's and card cage chassis. (Refer
to paragraphs 5-11 and 5-14,)
e. Remove side covers. (Refer to paragraph 5-4.)
f. On power and motor regulator PCA-A9, release the
1/4-turn fasteners and lower the PCA into its service
position.
g. Disconnect the carriage latch and detector assembly
wiring connectors.
h. Disconnect the head cable connectors and remove the
heads as outlined in paragraph 5-18.
1.
Disconnect the velocity transducer cable from
motherboard PCA-A7.
7925
b. Replace four bolts and lockwashers and secure
actuator assembly to the mainframe. Torque the bolts
to 80 inch-pounds.
c. Replace pack chamber assembly and connect door-
lock assembly cable. (Refer to paragraph 5-9.) Replace
the front frame assembly. (Refer to paragraph 5-7,)
d. Replace the cable shield on the underside of the
casting.
e. Connect coil ribbon cable to terminal board.
f. Reconnect the velocity transducer cable to mother-
board PCA-A7, install the heads as outlined in para-
graph 5-18, and reconnect the carriage latch and
detector assembly connectors.
Note: To install the heads, the head screw fas-
tener blocks (29, figure 6-7) must be re-
moved from the actuator.
g. Return power and motor regulator PCA-A9 to its
operating position and secure with the three 1/4-turn
fasteners.
h. Replace card cage chassis and card cage PCA's.
i. Restore ac power to the disc drive. Measure the abso-
lute filter air pressure as outlined in paragraph 2-13.
j.
Replace shroud and side covers.
j. Disconnect two leads on terminal board tabs that con-
nect to coil ribbon cable.
5-21.
VELOCITY TRANSDUCER AND
VELOCITY TRANSDUCER SHAFT
k. Remove the front frame assembly (refer to paragraph
5-7) and then remove the pack chamber assembly
(refer to paragraph 5-9.)
1.
Remove the cable shield on the underside of the
casting.
m. From the bottom of the mainframe, remove four bolts
and lockwashers (31 and 32, figure 6-2) that secure
the actuator assembly to the mainframe.
n. Grasp the top of the actuator assembly and lift it
straight up to release the guide pins from the holes in
the mainframe, then lift the assembly to the rear to
remove it from the disc drive.
To replace the actuator assembly, proceed as follows:
a. Position the actuator assembly over its mounting
space and seat the guide pins into the mating holes on
the mainframe. Attach the two capacitors to the coil
band shield barrier block and to ground. (Refer to
figure 6-7.)
5-10
The velocity transducer (1, figure 6-7) and the velocity
transducer shaft (3) are removed from the disc drive as
follows:
a. Perform the preparation for service outlined
III
paragraph 5-2.
b. Disconnect the ac power cord from the ac mains
power.
c. Remove the shroud. (Refer to paragraph 5-3,)
d. Remove the card cage chassis. (Refer to paragraph
5-14,)
e. Disconnect the velocity transducer cable from connec-
tor A7P2 on motherboard PCA-A7.
f. Loosen the setscrew
(4)
that secures the velocity
transducer shaft to the carriage assembly.
g. Using a slender tool (such as a 1/32-inch allen
wrench), push the velocity transducer shaft free from
the carriage assembly.