HP 7925D Service Manual page 216

PART III - ALIGNMENT AND ADJUSTMENT
In general, the alignment and adjustment procedures
given in section III of the main manual are applicable to
the HP 7925H. The only differences pertain to installing
the DSU (paragraph 3-8) and on-line checkout (paragraph
3-17). These paragraphs should be replaced with the fol-
lowing information.
A-74. INSTALLING THE DSU
WARNING
The equipment described in these in-
structions does not contain
operator-serviceable parts. To pre-
vent electrical shock, refer the fol-
lowing installation to service-trained
personnel.
To install the disc service unit (DSU), proceed as follows:
a. Perform the preparation for service procedure out-
lined in paragraph 5-2 of the main manual.
b. Ensure that the ac power cord is disconnected from
the ac mains power source.
c. Remove the shroud following the procedure outlined
in paragraph 5-3 of the main manual.
d. Remove the two nuts (6, figure A-14) that attach
the cable assembly (5) to the card cage cover.
Separate the cable from the cover.
e. Loosen the three screws that secure the preamp
shield and remove the shield.
f. Loosen the screws used to secure the card cage
cover to the card cage chassis and remove the
cover.
g. Remove jumper cable, part no. 13365-60006, con-
nected between data PCA-A1 and microprocessor
PCA-A2.
h. Remove data PCA-A1 and microprocessor PCA-
A2 from the card cage chassis.
i.
Install Head Alignment PCA, part no. 13354-60010,
into the card guides for Al. Ensure that the com-
ponent side of the PCA is facing towards the
right-hand side of the card cage chassis, as viewed
from the front of the disc drive. Push the PCA into
the connector on motherboard PCA-A7 until the
PCA is firmly seated.
j. Insert I/O Sector PCA, part no. 07925-60001, into
the card guides for A2. Ensure that the component
side of the PCA is facing in the same direction as
The component side of the head alignment PCA.
Push the PCA firmly in to the connectors on
motherboard PCA-A7.
k. Hang the DSU Test Module, part no. 13354-60005,
on the top outer edge of the card cage chassis as
shown in figure 3-4 of the main manual.
1. Connect 50-pin Jumper Cable, part no. 13354-
60012, between the 50-pin connector on the DSU
test module and J1 on the I/O Sector PCA.
m. Connect 20-pin Jumper Cable, part no. 13354-
60013, between the 20-pin connector on the DSU
test module and J1 on the head alignment PCA.
I
CAUTION
I
Do not plug or unplug any cables from
the data heads to read/write pre-
amplifier PCA-A6 or from the servo
head to track follower PCA-A5 while
the heads are loaded. Incorrect in-
formation can be written on the disc.
n. Connect the head cable connector from the head
alignment PCA to the head connector located at
the top of read/write preamplifier PCA-A6.
A-75. ON-LINE CHECKOUT
When all adjustments have been completed, remove the
CE disc pack. Set the power switch on the power panel
assembly to the 0 (off) position. Remove the DSU, head
alignment PCA, I/O sector peA, and related cabling. Re-
place data PCA-A1, microprocessor PCA-A2, reconnect
the cabling disconnected prior to alignment, replace the
shroud, and apply ac power.
The HP 7925H includes a self-test feature that provides a
go/no-go check of the controller hardware and also tests
certain functions of the disc drive. Self test can be invoked
in the following three ways:
• Automatically via a power-on or by setting the disc
drive RUN/STOP switch to RUN.
• Using the HP-IB INITIATE SELF-TEST command.
• Manually by activating the START switch on the
self-test panel located at the rear of the disc drive,
assuming that the controller is in Idle State 2 or 3.
Full details of self-test operation and readout interpreta-
tion are provided in Part IV of this appendix.
Following satisfactory completion of self test, perform an
on-line checkout in accordance with the diagnostic tests
supplied with the system.
A-35/A-36