Motorola Cm Radio Uhf2 Hp Information Manual

Chapter 3
TROUBLESHOOTING CHARTS
This section contains detailed troubleshooting flowcharts. These charts should be used as a guide in 
determining the problem areas. They are not a substitute for knowledge of circuit operation and 
astute troubleshooting techniques. It is advisable to refer to the related detailed circuit descriptions 
in the theory of operation sections prior to troubleshooting a radio.
Most troubleshooting charts end up by pointing to an IC to replace. It is not always noted, but it is...

3-2TROUBLESHOOTING CHARTS
1.0 Troubleshooting Flow Chart for Receiver RF (Sheet 1 of 2)
Problem in 12 KHz and 
25 KHz channel spacing
9V on
R310 (LNA)
OK
?Check
RX_ENNoGo to 
DC Section
Ye s
RX_EN
ON ?NoCheck Q306, Q300 
and U403Ye s
START
LOC_DIST
ON?Check Q304, D305 
and U403
LO
POWER
OK ?
Go to SYN 
Section
Ye s
Ye s No
No
Go
to A
3 V
to U301
Okay ?No
Check
LOC_DIST
Go to
DC Section
Ye s
Check D301-304
Replace IF Filters( FL304, FL301)
If problem in 25 KHz spacing
Check
TPI
Check 5V
on R337 )
5V
(IF...

Troubleshooting Flow Chart for Receiver RF (Sheet 1 of 2) 3-3
1.1Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)
3V
(IFIC -Vcc)
OK ?
Installation
OK ?
Ye s
Ye s No
No
A From
Check visually
all receiver
components
installation ?
Inject - 40dBm (CW)
to RF connector
Check Power on
C335 
RF
Power
> -28 dBM?Ye s NoCheck Power on
C337 
Go to 
DC Section
Check 
the component
Antenna to Mixer 
circuitry problem
Replace 
Q303, Q301
Check passive
componentsRF
Power
> -28 dBM?Ye s
NoReplace 
Q305, Q300,...

3-4TROUBLESHOOTING CHARTS
2.0 Troubleshooting Flow Chart for 40W Transmitter (Sheet 1 of 3)
START
Ye s
No
Check components between 
Q100 and RF output, 
Antenna Switch D104, 
D103, VR102 and Q106
No or too low power when keyed
Current
increase when 
keyed?
Check power settings, tuning 
& components between U103 
Pin 3 and ASFIC Pin 6 before 
replacing ASFIC
Control 
Voltage at 
TP150
>4Vdc?Check PA 
Stages
>4A
Voltage U103 
pin 5 = 
4.7V?
U103 Pin 3 
1.8Vdc
Check 9.3V 
Regulator 
U501
Ye s
Ye sNo
No
Ye...

Troubleshooting Flow Chart for 40W Transmitter (Sheet 1 of 3) 3-5
2.1Troubleshooting Flow Chart for 40W Transmitter (Sheet 2 of 3)
No
Ye s
Ye sNo
Check bias tuning 
before replacing 
U504
Check PA 
Stages
No or too low power when keyed
DC
Voltage
at Q101 & Q102 
base=0?
DC
Voltage
at U103 
Pin 8
Check U510
Check resistive network at 
Pin 9 and 10 of U103 
before replacing U101
Measure DC Voltage at Pin 2 & 3 of U5401
Pin 2 
Voltage 
0.62 x Voltage 
at Pin 1
Replace U5410
Pin 3 
Voltage 
0.51 x Voltage...

3-6TROUBLESHOOTING CHARTS
2.2Troubleshooting Flow Chart for 40W Transmitter (Sheet 3 of 3)
No
Ye s
Ye sNo
Check Final PA Stage
PA_Bias 
Voltage at 
R134
RF Voltage 
after C1044 
>100mV?
Voltage 
across R122 
>2V?
RF Voltage 
Q105 gate 
>1V?
RF Voltage 
Q100 gate 
>7V?
Check components 
between Q100 & 
antenna connector
Replace Q100
Check FGU (U5301)
Check components 
between C1044 & 
C1117
Check components 
between C117 & 
Q105
Check components 
between Q105 & 
Q100
No
No Ye s Ye s 1-4VSupply Voltage...

Troubleshooting Flow Chart for Synthesizer3-7
3.0 Troubleshooting Flow Chart for Synthesizer
5V
 at pin 6 of 
D200
Is
information
from
 uP U403
correct
?
Is
U200 Pin 47
at = 14.6VDC
?
Is
U201 Pin 19
4.5 VDC in TX?  
(at VCO section)
?
Sta rt
Visual 
check of the 
Board
OK?Correct
Problem
Check 5V
Regulator
U503
+5V
at U200
Pin’s
13 & 30
?
Is
16.8MHz
Signal at U200 
Pin 19
?
Check
Y201 and associated 
Parts
Are
signals
at Pin’s 14 &15 
of U200
?
Check 
R228Check R201
Is
U200
Pin 2  >4.5 VDC in 
Tx & 

3-8TROUBLESHOOTING CHARTS
4.0 Troubleshooting Flow Chart for VCO
Are Q200
Base at 2.9V 
Collector at 6.6V 
Emitter at 2.2V
Are U201 Pins
15 at 1.0V
10 at 3.9V
16 at 1.8V
Low or no RF Signal
at TP1
Visual check
of board
OK?
370mV DC at
U201 Pin 19
NO
YES
at base of Q200
NO
NO
NO YES
YESYESLow or no RF Signal
at input to PA
4.5V DC at
U201 Pin 19
Is RF available 
at C2060
YES
YESYES YES NO
NO
NO
NO
NO
Audio =180mVRMSat “-” Side of 
4.5VDC
at D205
If R211 and R12 are OK,
 then replace D205
Replace R211...

Troubleshooting Flow Chart for DC Supply (1 of 2) 3-9
5.0 Troubleshooting Flow Chart for DC Supply (1 of 2)
Since the failure of a critical voltage supply might cause the radio to automatically power down, 
supply voltages should first be probed with a multimeter. If all the board voltages are absent, then 
the voltage test point should be retested using a rising-edge-triggered oscilloscope. If the voltage is 
still absent, then another voltage should be tested using the oscilloscope. If that voltage is...

3-10TROUBLESHOOTING CHARTS
5.1 Troubleshooting Flow Chart for DC Supply (2 of 2)
Check VDC on
C5007
V=3.3V
?Check Voltage on 
C5041NoGo to Digital SectionYe s
9v