Technical Manual

10-7
10
Chart 5. DC Supply Failure
Is the
output on
U710-3
+5VDC?
No
Verify control
voltage at
Q106-4 is logic
low.
Control voltage
correct?
Check inverter
circuit of Q105
and R188.
No
Replace Q106.
Yes
Connect supply or
battery (B+) to radio
and turn
ON/OFF/VOLUME
CONTROL knob on.
Is B+ at
Q106-2?
DC Supply Failure
Synopsis
This failure implies a problem
with the DC power distribution.
It may relate to a battery
supply or one of the regulated
supplies. Basic failure modes
are as follows:
1) Fuse F1 blown.
2) Open in Battery contacts or
from flex circuit through P201.
3) Defective switch Q106.
4) Open in B+_SENSE through
control top switch or
6) Defective 20-pin compression
connector.
B+_SENSE not detected by µC.
5) Defective +5V regulator.
Check fuse F1.
Replace fuse.
Is
Fuse
good?
No
Check for open connection
between battery and RF
Board (J3), RF Board and
Controller Board (P201),
and between P201 and
Q106. Isolate and repair
open connection.
Yes
Yes
No
Verify B+ at
Q106-5.
Is B+ at
Q106-5?
Is +5VDC ± 5%
at C180?
Yes
Verify U709-2
> 2VDC.
U709
switched
on?
Yes
Check
continuity of
B+SENSE to
U709 and R184 pull-up,
and to J101-32.
No
No
Verify L119 continuity
< 1 Ω and solder
connection to board.
Yes
Verify Lx signal
per Fig. W1.
U709 running?
No
Yes
Verify integrity of
D104, C180, C174,
C175, and R186.
No
L119 good?
Continuity
OK?
Isolate and
repair open.
Replace front
cover assembly.
Replace U709.
Replace L119.
Yes
No
Yes
No
End
Yes
Yes
No
Verify SW_B+
at input to
U202 and
RESET signal is
logic low.
Signals
verified?
Replace U202.
Repair connections
back to the controller
board through P201.
Yes
No
Verify SW_B+
at input to
U710.
Replace U710.
Repair connections.
Yes
MAEPF-26018-O
No
Is the
output on
U202
+5VDC?
Signals
verified?