Table of Contents
Advertisement
7970B/7970C
7970-506
WRITE ENABLE
SENSING FINGER
SWITCH MOUNTING SCREWS
WRITE ENABLE SWITCH Sl
(ENERGIZES SOLENOIDI
WRITE ENABLE SWITCH S2
Adjustment Procedures
Figure 5-2. Write Enable Assembly
When the locking lever is working properly, it should be
possible to place the reel over the rubber with a minimum
of interference. When the locking lever is closed, positive
resistance should be encountered as the rubber is compres-
sed. 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, 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 screw. Repeat until tape reel
mounts firmly and does not slip.
5-19.
ELECTRICAL ADJUSTMENTS.
5-20.
The electrical adjustments of the tape unit are very
critical and must be performed in the following sequence:
a. Power supply adjustments.
b. Capstan motor offset current adjustment.
c. Capstan servo forward and reverse drive speed ad-
justments.
d. Capstan servo high-speed forward adjustment.
e. Capstan servo high-speed reverse adjustment.
f. Capstan servo ramp slope adjustment.
g. Reel servo adjustments.
Part 2
5-21.
POWER SUPPLY ADJUSTMENTS.
5-22.
Only one adjustment is provided for the three regu-
lated supplies. The adjustment control is located in the cir-
cuitry for the +12 volt supply but is adjusted to establish
the value of the +5 volt supply, which is held to a tighter
operating tolerance. The value of the +12 and -12 volt sup-
plies is established by a precision resistor network. The con-
trol is located on the power regulator printed-circuit assem-
bly. Voltage is correctly adjusted when the following con-
ditions are met:
a. +5 ± 0.050 Vdc. (Adjust to ±0.010 Vdc when ad-
justment is required.)
b. +12
±
0.360 Vdc.
c. -12
±
0.360 Vdc.
Note
Final reel servo adjustments must be made after
the capstan servo adjustments. The capstan speed
must be within tolerance in order to properly
adjust the reel servo. However, tension must be
maintained in order to make the capstan servo
adjustments.
If
the tape unit does not maintain
tension, perform the reel servo adjustments ini-
tially, complete the capstan servo adjustments,
and repeat the reel servo adjustments.
5-3
Advertisement
Table of Contents
