44
TROUBLESHOOTING FLOW CHART #6A
(VHF/UHF, Closed Architecture, No Receive Audio)
No
Audio
Audio at
R755?
Audio at
C306?
No
Audio at
Ext. Spk.
No
Audio at
Int. Spk.
Check Spk.
Flex, P701,
L705, L706
Ext.
Spk.
Selected
?
Check
P403
Audio at
U706, Pin 24,
Pin 2?
Check Spk.
Flex, P403,
L704, L706
Audio
Pin 4,
U706
?
Check Rx (Go to Troubleshooting chart #2A)
Check Flex P301, R775, C710
Check Control
Top Flex, P403
RF Controller
Flex P301, VOl SW.
Replace
U709
7.5V at
U709, Pin
8?
5V at
U709,
Pin 1?
Check U706,
C765, C763,
& C764
Replace Q702
6.8V at
base of
Q702?
5V at
Collector
Q702?
Rectify
Fault
Won't Unsq. Radio
Go To Controller
Troubleshooting
Chart #8A
P701
Flex
OK?
Press
Mon. Button
Is U706
Pin 20
Low?
Go To Controller
Troubleshooting
Chart #8A
5V at
U701 Pin
27?
If radio is in
PL mode, check
that PL code is
correct
Check Squelch
POT Setting
If Sq. Setting = 0
and radio does
not unsq., change
U701
Increase
signal level to
–47dBm.
Radio OK?
Check C769, C770,
C771, C772, C733
If OK, Replace
U706
Check
MCU U705
Check
C718
Rotate
VOL. POT.
Check Voltage at
C792 is changing.
Activity on U701
Data, SEL and Ck
Pins?
Noise at
C712 drops
when RF applied
?
If no audio, replace U701.
If weak audio, check
data sent to U701 is
changing as VOL. POT
adjusted before replacing
U701
Trace audio signal path
from jumper flex P301 to
Pin 16 of U701 for break
in audio path.
Audio
present at
U701
Pin 16
?
Audio
present at
U701
Pin 21
?
Audio
present at
U706
Pin 8
?
Is
U706
Pin 20
low?
Check RX.
Check U3, if RX
front end is
working.
NO NO
YES YES
NO
YES
YES NO
NO
NO
YES
NO
YES
NO NO
YESYES
NO NO NO
YES YES
YES
YES
YES
NO
YES
YES
NO
NO
YES
NO
NO
YES
YES
NO
NO
REV.
MAEPF-23275-O
Audio at U706
Pin 4, Pin 2
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