Table 4-2. Checkout/Troubleshoot the Receiver-Transmitter RT-1277/URC-92

TM 11-5820-873-34

Table 4-2.

Checkout/Troubleshoot the Receiver-Transmitter RT-1277/URC-92

STEP

ACTION

INDICATION

NEXT STEP

Remove top and bottom covers. Connect 115 VAC power cable

Step 2a

to POWER connector 1A8J3. Connect 50 ohm dummy load

through a thruline wattmeter to ANT jack 1A8J1. Connect a

known good Antenna Coupler CU-2229/URC-92 to

ACCESSORY jack 1A8J4. Set XMIT GAIN control fully

counterclockwise Set VOLUME control clockwise, 1/4 turn

Push VFO control in (off). Set DIM control fully clockwise.

Set mode switch to LSB.

ANTENNA COUPLER CONTROL meter lamp

Yes: step 2b

luminates.

No: step 17

Check pilot lamp and display.

Pilot lamp and display illuminate.

Yes: step 2c

No: step 29

Rotate DIM control one position counterclockwise. Then rotate Pilot lamp and display intensity dim, then go out. Yes: step 3a No: step 42

DIM control another position counterclockwise.

Meter lamp retains intensity, then goes out.

Set FREQ CONTROL switch to A. Set FREQUENCY A LOW FREQ LIMIT lamp illuminates and speaker noise Yes: step 3b No: step 44

controls to 1.5000 MHz. Rotate 100 KHz control through level decreases.

positions 4, 3, 2, 1, and 0.

Rotate 100 KHz control through positions 6, 7, 8, and 9.

LOW FREQ LIMIT lamp is out and receiver transmitter Yes: step 3c No: step 44

is enabled.

Set FREQ CONTROL switch to B. Set FRE QUENCY B LOW FREQ LIMIT lamp illluminates.

Yes: step 3d No: step 50

controls to 1.5000 MHz. Rotate 100 KHz control thru positions

4, 3, 2, 1, and 0.

Rotate 100 KHz control thru positions 6, 7, 8, and 9.

LOW FREQ LIMIT lamp is out.

Yes. step 3e No: step 50

Set FREQ CONTROL switch to A. Set FREQUENCY A

Noise is heard in speaker.

Yes: step 3f No: step 54

controls to 1.6000 MHz. Increase VOLUME control until noise

is heard in speaker.

Connect known good headphone to 1A1J3.

Noise is heard in headphone.

Yes: step3g No: step 280

Disconnect headphone. Connect known good handset.

Noise is heard in ear piece of handset.

Yes: step 3h No: step 289

Disconnect handset. Rotate RF GAIN control counterclockwise

Front panel meter reading increases to almost full

Yes: step 4a No: step 64

and observe meter.

scale deflection.

Return RF GAIN control to fully clockwise position and

Sidetone is heard in speaker.

Yes: step 4b No: step 77

VOLUME control to 1/4 turn clockwise. Connect a known good

CW key at the KEY jack. Set FREQUENCY A controls to

29.9950 MHz. Set mode switch to CW. Depress CW key.

Depress CW key and observe wattmeter.

Wattmeter indicates 100 W 10 W.

Yes: step 5a No: step 74

Connect oscilloscope across dummy load. Set oscilloscope to

Yes: step 5b No: step 163

Oscilloscope displays waveform similar to Fig.

.2 V/division. Set FREQUENCY A controls to 29.9995 MHz.

Set mode switch to LSB.

Connect microphone to MIC

4-2A, less than 2 V peak-to-peak.

connector. Key microphone and observe oscilloscope.

Set mode switch to USB. Key microphone and observe

Oscilloscope displays waveform similar to Fig. 4-2A, Yes: step 5c No: step 163

oscilloscope.

less than 2 V peak-to-peak.

Set oscilloscope to 50 V/division.

Key, and speak into

Oscilloscope displays waveform similar to Fig. 4-2A, Yes: step 5d No: step 165

microphone. Increase XMT GAIN control until no further

190 V peak-to-peak, maximum.

increase peak-to-peak voltage is observed.

Set mode switch to LSB Key and speak into microphone.

Oscilloscope displays waveform similar to Fig. 4-2A, Yes: step 5e No: step 175

Increase XMT Gain until no further

increase in peak-to-

190 V peak-to-peak.

peak voltage is observed.

Set mode switch to AM. Key and speak into microphone.

Oscilloscope displays waveform similar to Fig. 4-B, Yes: step 6a No: step 177

Observe oscilloscope.

modulated carrier signal.

Connect frequency counter to oscilloscope vertical amplifier

Frequency counter and front panel readouts agree for Yes: step6b No: step 185

output.

Connect oscilloscope across dummy load.

Set

each frequency.

FREQUENCY A controls to 1.6000 MHz. Turn XMT GAIN

Control fully counterclockwise. Key microphone. Starting with

100 Hz control, rotate each FREQUENCY A control through its

entire range.

4-2