Spindle Logic Pca-A8; Read/Write Preamplifier Pca-A6 - HP 7925D Service Manual

Spindle logic PCA-A8 (46, figure 6-2) is mounted in a card
cage located directly above the operator panel. To remove
this PCA, proceed as follows:
Removal and Replacement
b. Disconnect the ac power cord from the ac mains
power.
c. Remove the shroud. (Refer to paragraph 5-3.)
5-12. SPINDLE LOGIC PCA-A8
7925
d. Disconnect the interconnecting cable from jack Jl on
I/O Sector PCA-A2 (4).
e. Remove the three screws that secure the preamp
shield (1, figure 6-2) and remove the shield.
f. Loosen the two screws that secure the cable mount-
ing bracket (5) and the card cage cover (8). Remove
the bracket and cover from the card cage.
Note: Whenever I/O sector PCA-A2 is re-
placed, ensure the jumpers are in the
proper locations. (Refer to figure 4-27.)
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 door and remove the front shield (15,
figure 6-1).
d. Insert a blade-type screwdriver between the card cage
side and the spindle logic PCA retainer (44, figure
6-2).
e. Lightly pry inward the retainer .arm to extract the
screw head from its seating hole and lift out retainer.
f. Lift the PCA extractors outward and slide out the
spindle logic PCA.
To replace spindle logic PCA-A8, insert the PCA into the
card slot and firmly seat into the mating receptacle. Then
replace the retainer, ensuring that the screw heads are
secured in the seating holes.
g. On drive control PCA-A4 (11), simultaneously lift up
on the two PCA extractor levers and slide the PCA
up 5 cm (2 in.). Disconnect the data cable and fault
indicator cable from the PCA. If desired, remove the
drive control PCA-A4 from the card cage chassis.
h. To remove track follower PCA-A5 (12), disconnect the
servo head connector, then simultaneously lift up on
the two PCA extractor levers and slide the PCA up
and out of the card cage chassis.
5-13. READ/WRITE PREAMPLIFIER
PCA-A6
Note: Whenever track follower PCA-A5 is re-
placed, the data head alignment check
must be performed. (Refer to Section III,
Alignment and Adjustment.)
I
CAUTION
I
Ensure that the correct replacement
PCA is inserted into its corresponding
card slot, otherwise damage to the PCA
may result.
i.
Insert the replacement PCA into the card slot ensur-
ing that the component side of the PCA faces toward
the outer side of the disc drive. Reconnect any cables
disconnected during removal and then press the PCA
firmly into the receptacle until seated.
j. Install the card cage cover and the cable mounting
bracket and tighten the two mounting screws.
k. Install the preamp shield and secure with the three
mounting screws.
1. Replace the shroud. (Refer to paragraph 5-3.) Restore
the ac power to the disc drive.
5-4
To remove read/write preamplifier PCA-A6 (15, figure 6-2)
from a disc drive, proceed as follows:
I
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.
a. Perform the preparation for service outlined in para-
graph 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 three screws that secure the preamp
shield (1, figure 6-2) and remove the shield.
e. Disconnect all head connectors from PCA-A6.
f. Loosen (do not remove) the two screws which hold
the preamplifier retainer (44, figure 6-4) and push the
retainer upward. Pull the PCA out of the connector
and remove it from the disc drive.