37
VSX-918V-K
5
6
7
8
5
6
7
8
A
B
C
D
E
F
USB Troubleshooting
*
V
SX-91
8V
(A
W
X
8
977)
**
V
SX-
8
1
8V
(A
W
X9164)
Step 1: Connectors
Step 2: Power supply
C
N
401, C
N
1, C
N
2, C
N
3*, C
N
7**
To STEP 2
Are
the connectors
securely inserted
?
Insert the connectors
securely.
Check the patterns in
the path.
N
o
Yes
To STEP 1
Yes
Yes
Is there
any loose
connection
of C
N
1?
Check the PO
W
ER
PACK Assy.
N
o
C
N
1 (pins
8
, 9)
IC1 (pins 3, 4)
Is
the voltage
5
V
?
N
o
Yes
Is the base of
Q402 High? (about 5
V
)
[USBP
W
R]
Check C
N
3*, C
N
7**
pin 17.
[USB PO
W
ER]
N
o
N
o
Yes
Is IC1
abnormally
hot?
N
o
N
o
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
Yes
Replace Q401, or check the
circuit around Q401 and Q402.
Replace IC1.
The output and G
N
D may be
short-circuited. Check the path
between them.
Yes
Yes
Is
the voltage
5
V
?
N
o
Check the patterns in
the path.
IC402 (pins 1, 3)
1.
8
V
Regulator IC input
7
Yes
Is
the voltage
3.3
V
?
N
o
Check the parts and
patterns in the path.
IC462 (pins 37, 47) FLASH ROM
8
Yes
Is
the voltage
3.3
V
?
N
o
Yes
Check the parts and
patterns in the path.
IC4
8
1 (pins 1, 40)
Co-Processor
10
Is
the voltage
3.3
V
?
N
o
Yes
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
?
N
o
IC1 (pin 5)
3
Yes
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
?
N
o
Check the parts and
patterns in the path.
Is
the voltage
3.3
V
?
N
o
Yes
3.3
V
Local switch operation
Q401 (collector)
6
Is
the voltage
3.3
V
?
A
