Service manual

900 MHz Troubleshooting Charts 3-35
3.10 900 MHz Troubleshooting Charts
Audio at
Pin E4
U851?
Press PTT. Red
LED does not light
up.
PTT U409 Pin
53
low?
Press PTT
Q502-2 High?
Check
PB504.
Check
Q502-2
voltage.
LED
Q502,R501
OK?
ReplaceFaulty
Component.
Check
Accessories.
J403
OPT_SEL_1 &
OPT_SEL_2
Pin8&9
low?
Radio could
not PTT
externally.
U409
Pin 52, 6 low?
See FGU
Troubleshooting
chart.
LED should
light up.
Check MCU.
PTT
NO
YES
YES
No
No
NO
YES
YES
NO
YES
EXT
SPKR
EXT
PTT
INT
AUDIO
J403 Pin 9 low?
Pin 8 high?
ASFIC U404 Pin
14 & 15 high?
Check
Accessories
Check
U404.
Check
U420 Audio PA.
NO
NO
YES
YES
J403 Audio at
Pin2&Pin3.
Check Spk. Flex
Connection.
Audio at
Audio PA (U420)
input
(C447).
Audio from Pin 41
ASFIC, U404?
Check ASFIC
U404.
Check
Audio PA
(U420).
Check U351
LV ZIF.
Audio at
Pin 2
U404?
NO
NO
YES
YES
YES
NO
YES
Troubleshooting Flow Chart for Controller (Sheet 1 of 2
)
Audio from Pin F4,
HC, U851?
Check HC
U851.
YES
NO
NO
YES