AT&T Bell System Plant Series Adjustment Procedure page 12

SECTION 034-368-701
Fig. 8-Reel Motor Brake Showing the Drag Torque Adjusting Nut
(6) Operate the recorder in the rewind mode
and observe tape loops in both vacuum
chambers (Fig. 9). Both loops should oscillate
about the reverse (rear) loop sense photocells.
Minor readjustment of lRll for the supply vacuum
chamber or 2Rll for the take-up vacuum chamber
ma~· be necessary.
Page 12
3.09
Photosense Head
(1) Using TP2-35 (Fig. 6) as the 0-volt reference,
connect the KS-14510 Ll voltmeter between
TP2-35 and TPl-20.