Two motor control units are used in each antenna pedestal. These units are designated motor control
No. 1 and No. 2. Motor control No. 2, which is designated unit A1, consists essentially of terminal strips A1TB1 through
A1TB3, resistors A1R1 through A1R4, and capacitors A1C1 through A1C3. Motor control No. 1, which is designated unit
A2, contains servoamplifier A2AR1 (see Figure 5-8), radio interference filters A2FL1 through A2FL2, capacitors A2C1
through A2C4, resistors A2R1 and A2R2, and terminal boards A2TB1 and A2TB2. The detailed theory of operation of
the pedestal electrical components is contained in Section I.
A safety switch (item 56) on the riser base, with the positions SAFE and RUN, controls operating power
to the pedestal servo drive. When in the SAFE position, the servo drive is disabled.
When the servo drive is disabled, voltages are still present inside the riser base.
ADJUSTMENTS AND REPAIR - The components requiring adjustment on the antenna pedestal are:
synchros, cable-wrap potentiometer, limit switches, and the electric pressure brake. The synchro adjustment procedures
are contained in paragraph 2 of this section. Procedures for adjustment of the cable-wrap potentiometer, limit switches,
and electric pressure brake are contained in subsequent paragraphs as are procedures for repair of the pressure brake.
LIMIT SWITCH ADJUSTMENT
Release the electric brake.
Connect an ohmmeter across the azimuth limit resistor.
Rotate the pedestal CW to 270 degrees, as indicated on the azimuth vernier.
Loosen the three allen-head screws holding the upper section of the limit switch in position.
Slowly rotate the switch until the ohmmeter just indicates zero.
Tighten the retaining screws on the limit switch.
Rotate the pedestal CCW through 0 to 90 degrees, as indicated on the azimuth vernier.