Technical Manual

10-35
Chart 36. VHF/UHF Transmitter RF
No/Low Power
TX Current
> 500 mA?
RF at RF
Connector,J2
Pin 2?
Replace U105
NO
YES
RF at
Cathode of
CR108?
RF Present
at Anode
of CR108?
RF Present
at Pin 5 of
U104?
Replace U104
Check Antenna
Switch Biasing
Circuits, L122,
L105, U101
Check Components
Between C147
and L128
Check antenna
switch
YES
YES
YES
YES
NO
NO
NO
Is T5 On
at C153?
B+ at
U105, Pin 5
(VHF)
5,6 (UHF)?
Replace U105
7.5V at
U105
Pin 2.4?
Voltage
at U105
Pin 3?
RF Voltage
at U105,
Pin 1?
Check Components
Between U105
and U201. If No
Fault Found,
Go To FGU
Troubleshooting
Chart C.31
YES
YES
YES
YES
YES
NO
Go to DC Switch
Routine Chart C.36
Check B+, E1 & E101
(VHF), E1, E2, E3 &
E101, E104 (UHF) and
Power Supply
7.5V at
U105
Pin 2,4?
Voltage
at U105
Pin 3?
RF Voltage
at U105,
Pin 1?
7V at
Collector
of Q101?
5V at
U101,
Pin B4?
7.5V at
Emitter of
Q101?
Check L102, L103 (UHF)
L102, L130 (VHF)
Voltage at
Q101 Base
is B+ Less
0.7V?
Go to FGU No Lo
Injection/TX Not
Lock Routine
Chart #4A
Check Power
Supply
Replace Q101
Replace U101
Voltage at
U101 Pin A4
> 1V?
Replace U102
Check Detector
Circuit, CR102, (VHF),
CR101 (UHF), CR103,
R110, R111, U102
YES
NO
Replace U101
U101,
Pin E3, C1
About 2.5V
to 4V?
U101
Pin E2
About 3.5V
Pin C3
About 1.5V?
NO
YES
NO
NO
NO
NO
NO
YES
NO
YES
YES
NO
NO
YES
YES
NO
NO
MAEPF-26046-O