HP 7925D Service Manual page 248

PART V - REMOVAL AND REPLACEMENT
I
CAUTION
I
Whenever microprocessor PCA-A2 is re-
placed, ensure that programming jum-
pers VV360 through VV363 and VV312
through VV318 on PCA-A2 are correctly
programmed for HP 7925H operation as
follows. (The location of the jumpers is
shown in figure A-16.)
The majority of the removal and replacement procedures
contained in section V of the main manual are applicable
to
the HP 7925H. The only differences pertain to the
removal instructions for a) certain of the PCA's (para-
graph 5-10), and b) the fan on the card cage assembly.
These changes are discussed in the following paragraphs.
WARNING
The information given in this part is
intended for service-trained person-
nel. To avoid potentially serious elec-
trical shock, do not proceed further
unless qualified to do so.
A-89. CARD CAGE PCA'S
To remove any of the five card cage PCA's, A1 through A5,
proceed as follows:
VV360 -
IN
for rotational
position sens-
ing (RPS)
VV361 - Spare. An un-
used jumper
can be stored
here.
VV362 - OUT
VV363 - OUT
VV312 - OUT
VV314 - IN
VV316 -
IN
VV318 -
IN
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 removed 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 thqt secure the preamp shield
and remove the shield.
f. Loosen the two screws that secure the card cage
cover and remove the cover.
g. Disconnect all cables from the PCA to be removed
from the card cage chassis.
h. On PCA's Al and A2, pull up on the PCA extractor
and slide the PCA up and out of the card cage chas-
sis. On PCA's A3 through A5, simultaneously lift up
the two extractor levers and slide the PCA up and
out of the card cage chassis.
I
CAUTION
I
Ensure that the correct replacement
PCA is inserted into the corresponding
card guides, otherwise damage to the
PCA could result.
I
CAUTION
I
Whenever track follower PCA-A5 is re-
placed, the data head alignment check
must be performed. (Refer to section
III
of the main manual for details.)
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.
Replace the card cage cover and secure with the two
screws.
k.
Install the preamp shield and secure with the three
mounting screws.
1.
Connect the cable assembly to Data PCA-AI.
m. Attach the cable assembly to the card cage cover
using the two mounting nuts.
n. Replace the shroud as described in paragraph 5-3 of
the main manual.
o. Restore power to the disc drive.
A-gO. SELF-TEST PCA-A13
To remove the self-test PCA-A13 (13, figure A-22), pro-
ceed as follows:
A-75