Troubleshooting The Dsp Block - Pioneer VSX-74TXVi Service Manual

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7.1.3 TROUBLESHOOTING THE DSP BLOCK

Simplified diagnosis
Herein is described how to easily diagnose a defective part in the DSP Assy, only with operations of the main unit.
• Is the DSP Assy a cause of the problem?
Input a digital PCM signal (CD, etc.) and check if the sound is output, by switching AUTO SURR/STREAM DIRECT.
If the sound is output in PURE DIRECT (PCM DIRECT) mode but not in AUTO SURR or DIRECT mode, the DSP Assy
may be defective.
• If the sound is not output when Sound Delay is ON
If the sound is output without a problem when Sound Delay is OFF (0.0 fr) but an abnormality in the sound is detected
when Sound Delay is ON (0.1 - 6.0 fr), it is most likely that SRAM (IC106) or DECODER IC (IC104) in the 1st DSP block
is in failure.
Troubleshooting
• It is assumed that there is no loose connection or damage in the LCRs.
• Refer to "DSP Block Diagram."
Step 1: Connections
CN351, CN352
Are the
connectors securely
inserted?
Yes
To Step 2
Step 2: Power supply
A
5V input
CN352 (Pins 24-26)
No
Is the voltage
5V?
Yes
Check the output from the
DIGITAL MOTHER Assy.
B
IC351 (Pin 3) 1st Block 3.3V
No
Is the voltage
3.3V?
Yes
The output and GND may be short-
circuited. Check the path between
them.
C
DSP 3.3V
IC101 (Pin 7, etc.)
No
Check the parts and patterns
Is the voltage
3.3V? in the path.
Yes
5
6
No
Insert the connectors
securely.
Is there
No
any loose connection
at Pins 24-26 of
CN352?
Replace CN352.
Yes
Is IC351 No
abnormally hot?
Replace IC351.
Yes
6
7
D
LATCH 1
IC102 (Pin 20)
No
Is the voltage
3.3V?
Yes
E
LATCH 2
IC103 (Pin 20)
No
Is the voltage
3.3V?
Yes
F
Decoder
IC104 (Pin 8)
No
Is the voltage
3.3V?
Yes
G
FLASH ROM
IC105 (Pin 37)
No
Is the voltage
3.3V?
Yes
H
SRAM
IC106 (Pins 9, 27)
No
Is the voltage
3.3V?
Yes
A
VSX-74TXVi
7
8
Check the parts and patterns
in the path.
Check the parts and patterns
in the path.
Check the parts and patterns
in the path.
Check the parts and patterns
in the path.
Check the parts and patterns
in the path.
8
A
B
C
D
E
F
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