3-9. TROUBLESHOOTING PROCEDURES. (CONT)
TEST OR INSPECTION
13. Radio set works on some frequencies but not on others.
Frequencies 33.90 MHz, 45.20 MHz, 56.50 MHz, and 67.80 MHz are noncompatible
frequencies which cause transmitter quieting.
Reset all controls on control unit. If radio set still works intermittently, control unit or
receiver-transmitter is defective.
Replace control unit or receiver-transmitter (para 3-11).
14. Audio is distorted.
Check all electrical connectors for proper mating.
Reconnect all electrical connections properly.
Check aircraft intercommunications system for discrepancies.
Refer to applicable aircraft electronic maintenance manual for checks
and corrective action.
Reset all controls on control unit for transmit/receiver operation. If audio is still
distorted, receiver-transmitter is defective.
Remove and replace receiver-transmitter (para 3-11),
15. Reception and transmission are very weak,
Reconnect all connectors as required. Replace any defective cables.
If all cables and connectors are in proper condition, reset all controls on control
unit. If reception and transmission are still weak, receiver-transmitter is
Remove and replace receiver-transmitter (para 3-11).
16. Radio set does not operate in RETRAN mode.
Check squelch adjustment (SQ ADJ) on both receiver-transmitters.
Adjust SQ ADJ on both receiver-transmitters (para 3-4).