Table 4-3. Monitor Receiver Troubleshooting

TM 11-5825-270-23

Table 4-3. Monitor Receiver Troubleshooting-Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

POWER INDICATOR OFF

Step 1. Observe the NORM and ALARM indicators.

a. If the NORM or ALARM indicators are on go to step 2.

b. If the NORM and ALARM indicators are not on go to malfunction 3.

Step 2. Check the POWER lamp.

If the POWER lamp is correct remove the ac power from J2 and check the wiring between TB1-1 of the power supply

and DS1 (fig. FO-3).

SUPPLY VOLTAGES INCORRECT

Step 1. Check the voltage at TB1-1 and TB1-3 of the power supply. The voltage at TB1-1 will be +28 Vdc and the voltage at

TB1-3 will be +12 Vdc.

a. If the voltages a correct go to table 4-2 and perform the maintenance turn on procedure.

b. If voltages are not correct go to step 2.

Step 2. Check the voltage between TB1-5 and TB1-6 of the power supply. The voltage will be 34 Vac.

a. If the voltage is correct go to step 4.

b. If the voltage is not correct go to step 3.

Step 3. Check the voltage between terminals 1 and 4 of transformer T3. The voltage will be 115 Vac (or 220 Vac).

a. If the voltage is correct replace transformer T3. This procedure requires direct support maintenance personnel

(refer to chapter 5).

b. If the voltage is not correct remove the ac power from J2 and check the wiring between J2 and transformer T3 (fig.

FO-3).

Step 4. Remove the ac power at J2. Disconnect the leads at TB1-1 and TB1-3 of the power supply. Connect the ac power at

J2. Check the voltages at TB1-1 and TB1-3 of the power supply. The voltage at TB1-1 will be +28 Vdc and the

voltage at TB1-3 will be +12 Vdc.

a. If the voltages are correct go to step 5.

b. If the voltages are not correct replace power supply A4 (para 4-17).

Step 5. Remove the power at J2 and connect the leads to TB1-5 and TB1-6 of the power supply. Connect the ac power to J2.

Step 6. Remove the if. amplifier PCB, audio amplifier PCB, and rf PCB in turn, each time checking the voltages at TB1-1 and

TB1-3 of the power supply. The voltage at TB 1-1 will be +28 Vdc and the voltage at TB 1-3 will be +12 Vdc.

a. If the voltages are correct after one of the PCB's have been removed, the PCB just removed is at fault and must

be replaced.

b. If the voltages are not correct after the three PCB's have been removed, remove the ac power from J2 and check

the wiring connecting to TB1-1 and TB1-3 of the power supply (fig. FO-3).

NORM AND ALARM INDICATORS OFF

Step 1. Check the NORM and ALARM lamps.

a. If lamps are correct go to step 2.

b. If lamps are not correct replace the defective lamp and go to table 4-2 and perform the maintenance turn on

procedure.

Step 2. Set the POWER switch to OFF and check the dc continuity of contacts 4, 8 and 7 of relay K1 (fig. FO-3).

a. If good continuity is present go to step 3.

b. If good continuity is not present replace relay K1. This procedure requires direct support maintenance personnel

(refer to chapter 5).

Step 3. Check the wiring to K1-3 and K1-6 (fig. FO-3). If the wiring is correct go to malfunction 3.

CAUTION

When connecting signal generator to J1 of monitor receiver, connect a 1uF 25 V capacitor in

series with the signal generator output. Make sure that positive side of the capacitor is

connected to J1.

ANTENNA CHECK

Step 1. Disconnect the antenna from J 1 of the monitor receiver and connect the signal generator to J1.

Step 2. Set the signal generator frequency to the frequency of the monitor receiver. Set the signal generator output to 100 mV.

Step 3. Carefully adjust the frequency of the signal generator to get a reading of at least 0 dB on the CARRIER LEVEL meter.

a. If the reading is correct replace the antenna (para 4-10).

b. If the reading is not correct go to step 4.

Step 4. Disconnect the signal generator from J1 and connect the antenna to J1. Go to malfunction 13.

WRONG REMOTE ALARM INDICATION

Step 1. Remove the external connections at TB1-3, TB1-4 and TB1-5 at the back of the monitor receiver.

Step 2. Check for dc continuity between TB1-3 and TB1-4 and between TB-4 and TB-5. When the NORM indicator is on the

resistance between TB1-4 and TB1-5 will be 0 ohm. When the POWER switch is set to OFF the resistance between

TB1-4 and TB1-3 will be 0 ohm (fig. FO-3).

a. If the resistance readings are correct go to table 4-2 and perform the maintenance turn on procedure.

b. If the resistance readings are not correct replace relay K1. This task requires direct support maintenance

personnel (refer to chapter 5).

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