TROUBLESHOOTING TABLE-continued

TM 11-6625-2976-40

2-7. TROUBLESHOOTING TABLE. (CONT)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

Check voltage at P20 XTAL and PWR pins to the appropriate rf module (FO-3).

Step 3.

If voltage is ok, replace circuit card assembly A6 (para 2-19).

If voltage is Incorrect, go to step 4.

Check appropriate switches for malfunctions (FO-3).

Step 4.

Replace defective switches.

Check chassis wiring for a short or open circuits (FO-3).

Step 5.

Repair or replace faulty wiring.

2. incorrect carrier frequency at output.

No check.

Step 1.

Replace appropriate rf module (para 2-18).

3. Low power at output.

Check for loose coaxial cable connection between appropriate rf module,

Step 1.

attenuator, and antenna jack (FO-2).

Tighten any loose connections.

Check alinement of front panel ATTEN controls (para 2-15).

Step 2.

Realine misalined ATTEN controls.

No check.

Step 3.

Replace appropriate rf module (para 2-18). If checking GS or MB

mode, see note under MALFUNCTION 1, step 2.

4. VOR modulation or 9960 fm deviation performance test failure.

Step 1. Test master oscillator output in the following manner.

Connect oscilloscope (time base:.01 us; vertical: 1v/div; sync: INT) to J5

(FO-4). Verify ac signal 1 v peak-to-peak min. Connect frequency counter

to J5. Verify frequency 3.9322 MHz 400 Hz.

If voltage or frequency is incorrect, replace circuit card assembly A6

2-35