COMM CONT NUMBER 1 VOL CONTROL: Fully clockwise.
COMM CONT TEST: OFF.
DC POWER switch: OFF.
Set the COMM CONT TEST switch to position 1. Using multimeter AN/PSM-45,
measure the resistance on the MK-994/AR between J20A and J20B. This tests for a possible
shorted interphone line. Normally, you should get a reading between 12.6 and 15.4 ohms. If
your reading is not normal, T2 (see TM 11-5821-262-35, page 3-24) should be replaced and
the resistance measurement should be repeated.
Normal resistance measurement (12.6 to 15.4) tells you to perform the
protective device test. This test requires you to measure the DC voltage between voltage
regulator VR1 (TP-7-Emitter) and ground. Using the ME-26, measure the DC voltage to
ground. It should be (+) 19-21.0 V DC. If your reading is not normal, you should replace VR1
and repeat this step.
The last step in Subtest 1 will detect a possible broken lead or relay, K1.
Equipment settings are as follows:
COMM CONT TEST switch: Position 7.
DC POWER: OFF.
COMM CONT 2 SELECTOR switch: ICS.
Using the AN/PSM-45, measure continuity between J19A and relay K1, terminal
5 in COMM CONT 2. Normal reading is a zero ohms (short) reading. If your reading is
abnormal, you need to check for a broken lead.
Check relay K1, repeat the test between J19A and K1, terminal 7. Again, you
should read zero ohms (short) for a good indication. If you have an abnormal reading, you
would replace relay K1 and repeat the functional test (Lesson 1).
This completes Subtest 1. Repeat this test until you feel confident.
Subtest 2. Fault code 0|1 indicates a microphone amplifier AR1 problem.
Test equipment setup is the same as for the functional test. Equipment settings
are as follows:
COMM CONT NUMBER 1 SELECTOR switch: ICS.