Connect an a-c voltmeter across rotor terminals R1 and R2. Set the voltmeter to its 0- to 5-volt
Apply 115-volt, 60-cycle a-c power from a local source to stator terminals S1 and S2.
Carefully rotate the control transformer to obtain minimum voltmeter indication and secure the
clamps loosened in step a without moving the control transformer.
Remove the test connections and replace the original.
Position the orient control on the front panel of the Antenna Control Power Supply for the
differential to be zeroed to 0 degree.
Loosen the clamps holding the differential control transmitting synchro in place sufficiently to
permit rotating the differential by hand.
Remove all rotor and stator connections from the differential.
Connect a jumper between rotor terminals R1 and R3.
Connect a jumper between stator terminals R1 and S3.
Connect a 115-volt, 60-cycle, a-c source between stator terminals S2 and S3.
Connect a 0- to 250-volt a-c voltmeter, using the 0-to-250 scale, between the R2 and S2
terminals of the differential. Rotate the differential until the voltmeter indicates minimum.
Remove the 115-volt a-c source from terminals S2 and S3.
Disconnect the voltmeter from between terminals R2 and S2.
Remove the jumper from between rotor terminals R1 and R3.
Connect the 115-volt a-c source between rotor terminals S2 and S3.
Set the voltmeter to the 0- to 5-volt scale and connect across rotor terminals R1 and R3.
Rotate the differential until a null reading is obtained on the voltmeter and carefully secure the
clamps loosened in step b without moving the differential.