LOCAL OSCILLATOR A1500 ALINEMENT. - TM-11-5820-401-34-30329

TM 11-5820-401-.34-3/0967-LP-432-3060

CRYSTAL REFERENCE SYSTEM (CRS) TEST. (CONT)

4-15.

18. Set AN/GRM-114A VAR control (8) to OFF. (See test setup diagram

19. Connect AN/GRM-114A SCOPE probe A (see test setup diagram

(3) (see test setup diagram

, page 4-111), and probe B to ground. Set attenuated probe

to X10.

NOTE

Scope trace should be centered on screen. A slight ac component superimposed on the

horizontal trace is normal. If dc level varies higher than + 0.32 vdc or lower than -0.32

vdc, the CRS is defective. See the troubleshooting section.

In steps 20 and 21, scope trace should vary up to at least + 0.5 vdc and then down to at

least -0.5 vdc. If this does not happen, the CRS is defective. See the troubleshooting

section.

Slowly adjust AN/GRM-114A RF FREQUENCY MHz thumbwheels to 042250 0. Note scope trace.

20.

Slowly adjust AN/GRM-114A RF FREQUENCY MHz thumbwheels to 0417500. Note scope trace.

21.

LOCAL OSCILLATOR A1500 ALINEMENT.

4-16.

PURPOSE. If the local oscillator is operating at the correct frequency, the CRS will not ouput a dc

error signal. This procedure alines the oscillator by tuning its circuits to bring the CRS error signal as

close to zero as possible. The Crystal Reference System Test (paragraph 4-15) must be done prior to

performing this alinement.

TEST EQUIPMENT AND MATERIALS

Maintenance Kit MK-1978/VRC

Test Set AN/GRM-114A

Power Supply PP-1104(*)/G

TEST SETUP. Connect the equipment as shown in test setup diagram

R-442/VRC top cover. (See paragraph 2-7.) Connect P1004 to J1004 on the A1000 tray.

4-113