Pioneer VSX-821-K Service Manual page 41

5
D
REG1 (pin 3)
Is the voltage 5 V?
Yes
REG1 (pin 2)
Is the voltage 1.8 V output?
Yes
IC805 (pins 2, 3)
Is the voltage 5 V input?
Yes
IC805 (pins 6, 7)
Is the voltage 5 V output?
Yes
To Step 2
Step 2: Operation of USB Media Control IC
IC801 (pins 54, 55)
Is there a 12 MHz output?
Yes
CN802 usb_rx,tx (pins 4, 5)
Do usb_rx and usb_tx
communication
with main micom?
Yes
JACK801 (pins 2, 3)
Are there the waveforms
like figure?
Yes
Operation of IC801 is OK.
Go to step 3.
5
6
5 V input
No
Check the pattern in the path.
1.8 V output
No
Is REG1 abnomally hot?
Yes
5 V input
No
Is pin 4 (en) of IC805 low?
Yes
USB bus power
No
Check the parts and pattern in the
path of CN801.
xin/xout
No
CP803 pins 1, 2 (reset,rdy)
is high?
Yes
usb_rx and usb_tx should be high
No
during operation. Check the
pattern in the path of FRONT and
CPU Assys.
D+ and D- should have waveform
during normal condition. Check the
pattern in the path of IC801. etc..
No
IC801 (pin 44) -> IC803 (pin 38)
After turning the power on and
several seconds later,does SDCLK
change 12 MHz to 80 MHz?
Yes
Operation of IC801 is OK.
Go to step 3.
6
7
No
Replace REG1.
The output and GND may be
short-circuited. Check the path
between them.
No
Is pin 8 (fault) of IC805 high?
Yes
Replace IC805.
No
Check the CN704B of CPU Assy
and CN704A of FRONT Assy.
OK
Check the parts and pattern in the
path. Replace XTAL1, etc..
Fig. D+
X: 1 μS/div, Y: 2 V/div
initial communication [SDCLK]
DATA and ADDRESS lines
No
between SDRAM (IC803),
FLASH ROM (IC802), and IC801
are may not be connected.
VSX-821-K
7
8
No
Check the pattern in the path.
NG
Check the path to CPU Assy.
Fig. D-
X: 1 μS/div, Y: 2 V/div
8
A
B
C
D
E
F
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