Service manual

UHF Troubleshooting Charts 3-11
IF Signal
at L311?
No
RF Signal at
T301?
RF Signal at
C310?
No
RF Signal at
C307?
No
RF Signal at
C301?
No or
Check harmonic filter L101 & L102 and
antenna switch CR101, CR102, L104
Check filter between
C301 & C307; program
filter to schematic test
freq and check varactor
voltages
Inject RF into J101
Are varactor
voltages OK?
No
Yes
Check RF amp (Q301)
Stage
Check filter between
C310 & T301
Yes
Check T301, T302,
CR306, R308, R309,
R310
Yes
1st LO O/P
OK?
Locked?
Yes
Check FGU
Yes
Trace IF signal
from L311 to
Q302. Check for
bad XTAL filter
No
Yes
Q302 collec-
tor OK?
IF signal
present?
Before replacing
U301, check
U301 voltages;
trace IF signal
path
Yes
Check for 2.6
VDC
Is R5
present?
Check Q210, U201
(pin 48) voltages and
U247
No
No
No
Check U404 voltage.
U404canbeselectedby
MCU before replacing
U404
Check varactor filter
No
Yes
Yes
Yes
A
A
B
weak RF
Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)