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3-4
Troubleshooting Flow Chart for 25W Transmitter (Sheet 2 of 3)
2.1
Check S4440,
R4442 and R4443
Check Components
between U4402-2 Pin7
and Q4421. Check Resis-
tive Network at Pins 5 & 6
before replacing Q4421
DC
Voltage at
NO
U4402-1 Pin
3 = 8.8V?
YES
Measure DC Voltage at Pin 2 & 3 of U4401
Check Q4442 and
Resistive Network at
U4402-1 Pin 3
before replacing
U4401
DC
NO
Voltage at
U4402-2 Pin 5
<8.8V?
YES
Check Q4422
Check PA Stages
No or too low Power when keyed
NO
DC Voltage
at U4501
Pin 23 =0?
YES
>6
<2V
DC Voltage
at U4402-1
Pin 1?
2-6
Pin 2
NO
Voltage 0.62
* Voltage at
Pin 1?
YES
Pin 3
NO
Voltage 0.51
* Voltage at
Pin 1?
YES
DC
<2V
Voltage at
>6V
U4402-2
Pin 7?
2-6V
Check Final PA Stage
TROUBLESHOOTING CHARTS
If U4201 Pin 2 is high,
replace PCIC
Check Resistive Net-
work at Pins 2 & 3 of
U4402-1 before replac-
ing U4401
Replace U4401
Replace U4401
Check Components
between U4402-2 Pin7
and Q4421. Check
Resistive Network at
Pins 5 & 6 before
replacing Q4421