a. Defective audio distribution channels.
b. Defective antenna or cabling.
VHF volume control does not affect received au-
a. Defective VHF control panel.
b. Defective antenna or antenna cabling.
HF transmitted or received signal or sidetone
a. Defective HF receiver-transmitter.
b. Defective antenna cabling.
c. Defective HF control panel.
d. Defective audio control panel.
Course deviation indicator NAV flag remain in
view with receiver operating.
a. No reliable navigation signal on frequency
b. Defective VOR receiver.
c. Defective VOR control panel.
d. Defective antenna or cabling.
e. Defective NAV switching relays.
f. Defective pilots or copilots VOR switch on
g. Defective course deviation indicator.
No VOR audio tone heard in headset.
a. Defective VOR receiver.
b. Defective VOR control panel.
c. Defective audio control panel.
Marker beacon indicator light does not illumi-
a. Defective marker beacon indicator light.
b. No power to receiver.