Sony XBR-55X850D Service Manual page 30

FLOW
1-3. NO POWER DDCON/LDO
Case: BMFW2 structure
LDOs check
START
yes
Check Vcc voltage
no
C9xxx
Is voltage >3V?
yes
Check Enable pin
no
voltage
Is voltage >3V?
yes
Change LDO IC
Refer this list
XBR-55X850D/855D/857D, 65X850D/855D/857D, 75X850D/855D/857D
Check +3.3V_DDC_OUT
DDCON (IC9003)
1-2 No Power U-Com Failure
Case: BM1 + DPS structure
LDOs check
START
yes
no
Check Vcc voltage
C9xxx
Is voltage >3V?
yes
no
Check Enable pin
voltage
Is voltage >3V?
yes
Change LDO IC
Refer this list
TROUBLE SHOOTING
Check +3.3V_DDC_OUT
DDCON (IC409)
1-2 No Power U-Com Failure
30