HP 7901A Operating And Service Manual page 51

7901A
5-48.
CARRIAGE VERNIER ADJUSTMENT.
a. Loosen the two mounting screws for the position scale
on the upper deck assembly.
b. Use the Disc Service Unit to position the carriage at
cylinder 100.
c. Using 0.005-inch thick Mylar shim, adjust the gap be-
tween the carraige vernier and position scale to 0.005
+
0.005 - 0.001 inch.
d. Return the carriage to cylinder 000.
e. Adjust the position scale so that the line marked "0"
aligns with the line marked "0" on the carriage vernier.
Tighten the two mounting screws.
f. Use the Disc Service Unit to incrementally seek be-
tween 000 and 202 to verify that the position scale
does not touch the vernier.
Maintenance
5-49. TROUBLESHOOTING.
5-50. Troubleshooting the disc drive is accomplished by
performing the appropriate diagnostic program procedures
in the Manual of Diagnostics. More detailed troubleshooting
can be accomplished by referring to flow diagrams, sche-
matics, PCA component locations diagrams, and integrated-
circuit pack diagrams given in figures 5-11 through 5-44.
Replaceable parts for individual PCA's are listed in tables
5-4 through 5-15.
5-51. REMOVAL AND REPLACEMENT.
5-52. Replaceable parts are listed in section VI. Removal
is accomplished by using figures 6-1 through 6-6 in conjunc-
tion with tables 6-1 through 6-6. Each figure and associated
table lists replaceable items in order of removal. Replace-
ment is made in the reverse order.
5-13