HP 7970B Operating And Service Manual page 14

Performance Checkout
e. Reel Retaining Knob: With the locking lever re-
leased, the reel should slip over the rubber grip ring easily,
and it should be possible to easily rotate the reel. When the
lever is closed, positive resistance should be felt as the rub-
ber is compressed. In the locked position, it should not be
possible to move the reel by hand. If slippage is suspected,
place a piece of masking tape on the reel, and another on
the hUb. A mark placed in alignment on both pieces of tape
should not become misaligned by more than 1/8 inch in 16
hours of operation. To correct tape reel slippage, release
locking lever and loosen the pozidrive screw, rotate the reel
retainer knob clockwise, and tighten the screw. Repeat until
tape reel mounts firmly and does not slip.
3-11. OPERATOR CONTROL CHECKS.
3-12. Verify position of 115/230 volt selector switch;
connect unit to appropriate power source and check the
following operating modes.
3-13. TAPE LOADING AND WRITE ENABLE. Place a
reel of tape (with write enable ring) on unit and thread with
the power switch on. After threading tape, press LOAD and
verify that the following takes place.
a. Tape tension is established. RESET indicator il-
luminates.
b. WRITE ENABLE indicator illuminates.
c. Tape moves forward at 20 ips to load point tab
(BOT tab).
d. LOAD indicator illuminates.
3-14. ON-LINE TRANSFER AND RESET. Place the
control and status PC assembly unit select jumper in the
OFF pin (this is not the same as OFF on unit select option)
and load tape. Following completion of a load sequence
with tape positioned at load point (LOAD indicator on),
press ON-LINE and verify that unit will respond to external
commands. Pressing ON-LINE while load point search is in
process will also result in ON-LINE operation upon com-
pleting the search (LOAD indicator is ON). While ON-LINE,
the unit will not respond to local controls with the excep-
tion of RESET.
3-15. DYNAMIC BRAKING AND RECOVERY FROM
POWER FAILURE. Place unit in rewind mode after tape is
well into take-up reel. When full rewind speed is reached,
turn power switch off to simulate power failure. Tape should
stop without any damage to tape. Proceed with recovery to
on-line status by following normal load sequence. Except
that when tape unit goes into the load point search mode,
load point tab may be simulated by pressing the RESET
button. This can then be followed by an on-line command.
3-16. REWIND OPERATION. The REWIND control is
operational only while the unit is in the reset state which
permits local control. The rewind command will override
3-2
7970B/7970C
the load command and will return the tape to the load point
position (LOAD indicator on with tape stopped). Rewind
may be terminated prior to load point by pressing RESET.
Transfer to on-line is also possible immediately following
this sequence.
3-17. SERVICE SWITCHES AND ACCESSORY
CHECKS.
3-18. There are three service switches incorporated in the
capstan servo card. These together with the REWIND and
LOAD controls provide a means of operating all five drive
modes for service and
lor
adjustment purposes. There is no
capability for cyclic drive operation.
3-19. The HP 13191A Control and Status Test Board is
available for use with the tape unit. With this test board it
is possible to completely adjust and verify the performance
of the control and status function of a tape unit under off-
line conditions. Complete operating details are included with
the test board. The HP 13191A Control and Status Test
Board provides normal drive modes as well as cyclic pro-
gramming which is suitable for adjustment of the capstan
start/stop ramp. The board also includes status indicator
lamps to verify all normal status functions. The test board
is installed in the connector of the tape unit control and
status PCA.
3-20. TAPE PATH EVALUATION.
3-21. With undamaged tape threaded on the tape unit
and with the unit in the appropriate operating mode, evalu-
ate the following characteristics of the tape path.
a. Capstan Height: Capstan height should be such that
the tape is guided equal distance in from the outer and inner
edge of the capstan. The air escape grooves provide a means
for judging.
b. Tension Position: Arms should be aligned with the
centering marks on the rear of the casting. Position is ac-
ceptable provided the arm is not out of location by more
than the diameter of the arm.
c. Tape Tracking Over the Tape Guides: Tracking
over the guides should be smooth with no evidence of edge
forces anywhere in the tape path. Transverse reflected light
may be used to assist in judging. Light reflections across
the 1/2-inch width of the tape should not be bent due to
points of stress.
d. Photosense Position: Face of photosense head as-
sembly should be parallel to the path of the tape and posi-
tioned 1/8 inch from the tape.
3-22. POWER SUPPLY VOLTAGE CHECKS.
3-23. Both regulated and unregulated supplies should be
checked for the following specifications.
Part 2