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

TM 11-5820-873-34

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

STEP

ACTION

INDICATION

NEXT STEP

keyed--check 1A3A5Q1 and associated circuitry )

288

Replace and/or repair Display CCA 1A1A3. Use conventional

---

troubleshooting methods for CCA repair. (If one or more

segments are incorrect--check 1A1A2J1 for proper connection.)

289

Replace and/or repair Decoder CCA 1A1A2. Use conventional

---

troubleshooting methods for CCA repair.

290

Replace and/or repair Audio CCA 1A3A4. Use conventional

---

troubleshooting methods for CCA repair.

291

Replace and/or repair Speaker Driver CCA 1A1A1. Use

---

conventional troubleshooting methods for CCA repair.

292

Replace and/or repair Filter Module Assy.

1A5.

Use

---

conventional troubleshooting methods for repair.

293

Replace and/or repair RF Power Amplifier Assy. 1A7A1. Use

---

conventional troubleshooting methods for repair.

294

Replace and/or repair Sideband Generator CCA 1A3A3.

---

Perform ALC, ACC, Carrier Null, and Balanced Modulator

adjustments. Use conventional troubleshooting methods for

repair. (If no CW sidetone--check 1A3A2C28 and 1A3A3C31.)

295

Replace and/or repair IF Filter CCA 1A3A2. Perform 2nd IF

---

adjustment. Use conventional troubleshooting methods for

CCA repair. (If low transmit audio and low receive sensitivity--

check diodes 1A3A2CR1 thru 1A3A2CR16).

296

Replace and/or repair Spectrum Generator CCA 1A4A1.

---

Perform 17 MHz, 20 MHz, and 21 MHz adjustments. Use

conventional troubleshooting methods for CCA repair. (If tone

or beat note Is heard in AM receive--check 1A4A1Q3.)

297

Replace and/or repair Synthesizer Mother Board 1A4A6. Use

---

conventional troubleshooting methods for repair. (If 3rd local

oscillator blanks only every other time--check 1A4A6Q2.)

298

Replace and/or repair VHF Mixer CCA 1A3A1. Perform 1st IF

---

and IF Gain adjustments. Use conventional troubleshooting

methods for CCA repair. (If loss of receive or receive

sensitivity--check 1A3A1Q2 and associated circuitry.)

299

Replace and/or repair Translator CCA 1A4A3. Perform VFO,

---

21 MHz, 19.45 MHz, 81.25 MHz, 100.75 MHz Bandpass Filter,

2nd L.O., and Output Level adjustments. Use conventional

troubleshooting methods for CCA repair. (If no transmit or

receive--check oscillator circuit, 1A4A3Q7 and associated

components.)

300

Replace and/or repair VHF VCO CCA 1A4A5. Perform Band 0,

---

Band 1, Band 2, and 1st L.O. adjustments. Use conventional

troubleshooting methods for CCA repair. (If off frequency--

check 1A4A5Q1 and 1A4A5Q2.)

301

Replace and/or repair Low Digit Generator CCA 1A4A2.

---

Perform VCO adjustment. Use conventional troubleshooting

methods for CCA repair. (1 If incorrect frequency--check

1A4A2CR14 and 1A4A2U5; 2. If 1A4A2U3 has a high output--

check that all are switching between low and high, if one input is

not switching then

4-21