OVERVOLTAGE PROTECTION

TM 11-5820-918-13

Table 5-3.

Troubleshooting Guide - Continued

Indication

Location/Cause

Indicates in any of 1024 DC power supplies or

System fault indicator lights

fault synthesizer. Perform synthesizer and

red lamp.

1024 DC power supply performance tests.

Refer to paragraphs 5-23, 5-24, and 5-31.

10.

Refer to table 3-1 (Section 3) and replace

Battery fault indicator lights

batteries (or complete battery pack) if

red lamp.

necessary.

5-10. OVERVOLTAGE PROTECTION. The 1024 and 4011 power supplies incorporate

an overvoltage protection device, shown in figures FO-18 and FO-27. The overvoltage

device accomplishes circuit protection by effectively short circuiting the output ter-

minals of the power transformer when the trip voltage limit is exceeded. The over

voltage device is connected across the 11 volt terminals and trips at 17 volts. When

the trip voltage is exceeded, the input power fuse is normally blown. This con-

dition should be noted when troubleshooting and line voltage checked before trying

to turn on the transmitter.

5-11. OVERHEATING PROTECTION. Overheating conditions in the 5018 unit are

sensed by a thermal cutoff switch, U1 (figure FO-21/1). This switch is located on

the 5018 power amplifier RF assembly and activates when temperature exceeds 215F

(101C) to disable the 27 VDC power supply to the amplifier.

ADJUSTMENT

PROCEDURES

5-13. GENERAL. All initial adjustments to the transmitter are made at the factory

before shipment. These procedures are provided for use following repair or as re-

quired during the performance verification test.

WARNING

Use extreme care when making internal adjustments with power on. Po-

tentially lethal voltages are present in the transmitter.

5-14. 1024 POWER SUPPLY ADJUSTMENT (S/N 400101 and on). The 1024 has only

one power supply adjustment. This adjustment involves connecting of a low line tap

for line voltage variations that are below acceptable limits. The 1024 operates satis-

factorily when the main line power is between 110 and 125 volts (for 115V position of

voltage select toggle switch) or 215 to 250 volts (for 230V position of toggle switch).

(Refer to figure FO-18.) Use of the low line tap (220- 105) is only necessary if line

voltages lower than 110V (or 215V) are expected. To make this adjustment, discon-

nect wire at TB1, pin 1 that goes to switch S1, and connect wire to TB1, pin 2 (figure