(Vhf/Uhf Transmitter Rf) - Motorola Handie-Talkie MTX Series Theory/Troubleshooting Manual

No/Low Power
TX Current
> 500 mA?
YES
Replace RF Jack,
Jack, S101
S101
Check Components
YES
Between C147 Cathode of
and L128
Check Antenna
RF Present
YES
Switch Biasing
Circuits, L122,
L105, U101
YES RF Present
Replace U104
Replace U105
Replace U101
34
TROUBLESHOOTING FLOW CHART #1A

(VHF/UHF Transmitter RF)

NO
YES
RF at RF
Pin 3?
NO
RF at
CR108?
NO
at Anode
of CR108?
NO
Check Components
Between U105
and U201. If No
Fault Found,
at Pin 5 of
U104? Go To FGU
Troubleshooting
Chart #4A
NO
U101
Pin 3
NO
About 3.5V
Pin 6
About 1.5V?
YES
NO
Is T5 On
at C153?
YES
B+ at
U105, Pin 5 NO
(VHF)
5,6 (UHF)?
YES
7.5V at 7.5V at
NO
U105 U105
Pin 2.4? Pin 2,4?
YES
Voltage Voltage
NO
at U105 at U105
Pin 3? Pin 3?
YES
NO RF Voltage RF Voltage
at U105, at U105,
Pin 1? Pin 1?
YES
Replace U105
U101,
YES
Pin 2,7
About 2.5V
to 4V?
NO
Check Detector
Circuit, CR102, (VHF),
CR101 (UHF), CR103,
R110, R111, U102
Go to DC Switch
Routine Chart #3A
Check B+, E101 (VHF)
E101 and E104 (UHF)
and Power Supply
7V at
YES
Check L102, L103 (UHF)
Collector
L102, L130 (VHF)
of Q101?
NO
Go to FGU No Lo
5V at
NO
Injection/TX Not
U101,
Lock Routine
Pin 16?
Chart #4A
YES
7.5V at NO
Check Power
Emitter of
Supply
Q101?
YES
Voltage at
YES
Replace Q101
Q101 Base
is B+ Less
0.7V?
NO
YES
Voltage at U101
Replace U101
Pin 14 > 1V?
NO
Replace U102
MAEPF-23268-O