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7970Bj7970C
Adjustment Procedures
SECTION V
ADJUSTMENT
5-1.
INTRODUCTION.
5-2.
This section provides adjustment procedures for
the tape transport of the HP 7970Bj7970C Digital Magnetic
Tape Units. The adjustment procedures consist of mechan-
ical adjustments, power supply adjustments, capstan servo
adjustments, and reel servo adjustments.
5-3.
TEST EQUIPMENT REQUIRED.
5-4.
The following test equipment or equipment with
equivalent capacity is required to perform the adjustments.
a. A means of dynamically operating the tape unit at
drive rates specified in the procedure. The HP 13191A Con-
trol and Status Test Board is available as a service accessory
and will meet the needs for all adjustments. Computer op-
eration is also suitable.
b. HP 140A Oscilloscope.
c. HP 1421A Time Base and Delay Generator (for
HP 140A).
d. HP 1402A Dual-Trace Amplifier (for HP 140A).
e. HP 5245L Counter.
f. HP 5265A Digital Voltmeter Plug-In (for HP
5245L).
5-5.
In addition to the listed test equipment, Transport
Test Tape HP part number 5080-4525 is required.
5-6.
MECHANICAL ADJUSTMENTS.
5-7.
Transport mechanical adjustments consists of tape
roller, reel servo arm, write enable switch, and reel retaining
knob adjustments.
5-8.
TAPE ROLLER.
5-9.
All tape rollers are precision referenced to the step
in the shaft on which they are mounted. Under no circum-
stances should any adjusting shims be placed between the
inner bearing and this step. Shimming is done at the outer
end of the roller. Assembly should consist of one shim next
Part 2
PROCEDURES
to the bearing, then the preload washer, followed by shims
to remove all end play. Proper preload will exist when there
is one shim beyond the number required to just remove the
end play. Shim thickness is 0.005 inch, nominal.
5-10.
Tape roller loading is critical. Tape roller loading
must be performed whenever the tape roller is dismantled
or repaired. The exploded tape roller assembly is illustrated
in figure 5-1. To obtain the proper tape roller loading, pro-
ceed as follows:
a. Assure that brass nut (figure 5-1, 8) is torqued to
5 inch-pounds.
b. Install assembly components as indicated in figure
5-1. Use Retaining Ring Pliers (Waldes 18-23; Industrial Re-
taining Ring Corp P100; or equivalent). Avoid distorting re-
taining ring.
c. Check tape roller bearing assembly
(6)
end-play.
Add'/remove flat washers (3 or 2) until end-play is just
removed.
d. Spin bearing assembly and check for drag. The
tape roller must spin freely.
If
the tape roller does not spin
freely, loading is excessive; recheck end-play clearance.
5-11.
TENSION ARM.
5-12.
The tension arm adjustments consist of properly
positioning the photosense assembly relative to the photo-
sense mask and positioning the limit switches relative to the
tension arm.
5-13.
TENSION ARM PHOTOSENSE. This adjustment
is critical. Adjust as required to assure that the tension arm
photosense mask does not touch the photosense lamp and
cell assembly. There should be a nominal clearance of 0.010
inch minimum between the cell and the outer side of the
mask.
5-14.
TENSION ARM LIMIT SWITCHES. The limit
switch mounting bracket pivots on the screw that mounts
the tension arm rubber stop. The hole for the adjacent screw
is elongated to provide limit switch positioning adjustment;
this screw locks the mounting bracket in position after com-
pletion of the adjustment. Mounting holes for the micro-
switch are also elongated, providing slight additional limit
switch adjustment movement. To position the limit switch,
rotate the bracket and/or adjust height position to achieve
the following conditions:
a. When arm is fully against bumper, the roller on the
microswitch should be approximately at the high point of
the arm diameter without being over center.
5-1
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