HBD-NF620, HBD-NF720 - Sony Audio Service Manual (repair manual). Page 2

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HBD-NF620/NF720
2
TROUBLESHOOTING
1. Power 
check 
fl ow
The power is turned on.
Check that a sound is 
outputted normally.
Check that [Audio Settings] -
[Audio output] in the menu 
screen is “Speaker”.
Check that the output voltages of the 
SWITCHING REGULATOR are the following 
value.
CN301 pin 1:  12 V (A+12V)
CN301 pin 2:  12 V (UNSW12V)
CN301 pin 3:  12 V (FEUNSW12V)
CN301 pin 8:  6 V (UNSW6V)
Check that the following fuses are not damaged.
F5303/F5305/F5306/F5307/F1301
Check the following power control signal in the 
power on state. (Normally voltage: +3.3 V)
MB-149 board
IC6301 pin 36 to 38 (PCONT1 to PCONT3)
NG
OK
OK
OK
Check the related IC on the MB-149 board.
OK
OK
Check each voltage with reference to the 
schematic diagrams, and check that there is 
no problem in them.
OK
Check that a picture is outputted normally.
NG
Optimize the speaker settings.
NG
Check that the drive is 
operating normally.
– Continued on next page –
OK
Refer to the “2-1. Flow of drive section check” 
on page 6 on original service manual.
NG
OK
Check that harness is inserted 
normally.
When harness is inserted normally, 
exchange the SWITCHING 
REGULATOR.
Exchange the damaged fuse.
Exchange the complete MB-149 board, 
when the power is not turned on, even
 if you exchange fuses.
NG
NG
Power supply IC is damaged.
Exchange the power supply IC.
NG
Refer to the “2. Video check 
flow” on page 4.
NG
Exchange the IC6301.
Part No. 
Description
A-1857-997-A  IC   R5F3650KCDFB
  
(for 
SERVICE)
NG
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