AT&T Bell System Plant Series Adjustment Procedure page 8

SECTION 034-368-701
TPI TP2
Fig. 6-Control Unit Showing Potentiometer and Test Point Locations
across the read-write heads for normal tape
operations.
(10) Place a distinguishable pencil mark or a
small piece of tape on the front face of
the capstan for use as a reference point while
using the stroboscope. The mark should be
placed near the periphery of the capstan but not
touching the outer rubber part.
(11) Operate the recorder in forward operation.
(12) Set the stroboscope flashing rate as closely
as possible to 139 flashes per minute. With
the stoboscope flashing light directed on the
rotating capstan, adjust R26 on the capstan
servo printed circuit board CS~ (Fig. 6) until
there are three essentially stationary images of
the mark on the front face of the capstan.
Capstans rotation should now correspond to 46.3
rpm.
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(13) Operate the recorder in reverse operation
and repeat the procedure in (12) except
adjustment shall be made on R27 to obtain proper
capstan speed in reverse.
(14) Recheck capstan speed in forward operation
and readjust R26 if necessary.
( 15) Remove power from the recorder and
disconnect the patching cords from TP2.
2.08
Reel Servo Speed:
Individual reel servo
systems control the motions of the supply
and the take-up reel motors which are functional
in maintaining the proper amount of tape within
the vacuum chambers. The amplitude of tape loop
oscillations in the vacuum chambers (Fig. 2) shall
not exceed 7 inches. This requirement can be
checked by observing the tape loop in the take-up
reel vacuum chamber during forward tape motion.
Operate the recorder in reverse tape motion and