Service manual

37
VSX-918V-K
5
6 7 8
5
6 7 8
A
B
C
D
E
F
USB Troubleshooting
* VSX-918V (AWX8977)
** VSX-818V (AWX9164)
Step 1: Connectors
Step 2: Power supply
CN401, CN1, CN2, CN3*, CN7**
To STEP 2
Are
the connectors
securely inserted
?
Insert the connectors
securely.
Check the patterns in
the path.
No
Ye s
To STEP 1
Ye sYe s
Is there
any loose
connection
of CN1?
Check the POWER
PACK Assy.
No
CN1 (pins 8, 9)
IC1 (pins 3, 4)
Is
the voltage
5 V ?
No
Ye s
Is the base of
Q402 High? (about 5 V)
[USBPWR]
Check CN3*, CN7**
pin 17.
[USB POWER]
No
No
Ye s
Is IC1
abnormally
hot?
No
No
5 V input (For internal circuit)
3.3 V Regulator IC input
3.3 V Reg. output
3 V to 5 V Converter
1
2
Ye s
Replace Q401, or check the
circuit around Q401 and Q402.
Replace IC1.
The output and GND may be
short-circuited. Check the path
between them.
Ye s
Ye s
Is
the voltage
5 V ?
No
Check the patterns in
the path.
IC402 (pins 1, 3)
1.8 V Regulator IC input
7
Ye s
Is
the voltage
3.3 V ?
No
Check the parts and
patterns in the path.
IC462 (pins 37, 47)
FLASH ROM
8
Ye s
Is
the voltage
3.3 V ?
No
Ye s
Check the parts and
patterns in the path.
IC481 (pins 1, 40)
Co-Processor
10
Is
the voltage
3.3 V ?
No
Ye s
Check the parts and
patterns in the path.
IC461 (pins 1,3,9,14,27,43,49)
SDRAM
9
Is
the voltage
3.3 V ?
No
IC1 (pin 5)
3
Ye s
3.3 V Local switch
Q401 (emitter)
5
Is
the voltage
3.3 V ?
Check the parts and
patterns in the path.
IC351 (pin 20)
4
Is
the voltage
5 V ?
No
Check the parts and
patterns in the path.
Is
the voltage
3.3 V ?
No
Ye s
3.3 V Local switch operation
Q401 (collector)
6
Is
the voltage
3.3 V ?
A