Sony XBR-55X850D Service Manual page 39

FLOW
3-2. NO SOUND (AUDIO)
No Sound
Audio
Replace B Board
Finish
XBR-55X850D/857D, 65X850D/855D/857D, 75X850D
3-3. NO SOUND (POWER OFF CHECK)
Power Off Check
From 2-2
(1) B / DPS Board Yes
PVDD-GND short ?
No
(2) B / DPS Board
Yes
LDO out short ?
No
(3) B / DPS Board
Yes
Fuse broken ?
No
Replace B Board
BMFW2 Board
(1) PVDD-GND short check
Measure impedance between PVDD and GND at
capacitor C7881.
If impedance is <100Ω NG
(2) LDO out short check
Measure impedance between +3.3V and GND at C7880.
If impedance is <100Ω NG
(3) Fuse open check
Measure impedance of fuse
F7702 5A (12.5V or 19.5V)
If fuse open NG
TROUBLE SHOOTING
Power Off Check
From 3-1
Measure the Speaker
Yes
impedance by multi-meter
Less than 3Ω ?
No
Confirm the speaker
Yes
harness
Replace Speaker Harness
Cut or shorted
to the chassis ?
No
Return to 2-2 or 3-1
DPS Board
(1) PVDD-GND short check
Measure impedance between PVDD and GND at
capacitor C7932, C7914.
If impedance is <100Ω NG
(2) LDO out short check
Measure impedance between +3.3V and GND at C7913,
C7931.
If impedance is <100Ω NG
(3) Fuse open check
Measure impedance of fuse
F7700, F7701 5A (12.5V or 19.5V)
If fuse open NG
Replace Speaker
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