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1.0 No Sound Output, Different Av Cable Didn't Help

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I have a 1.0 xbox that was working perfectly up until the sound output quit. I have tried different cables, different TVs but...nothing.

I'm thinking hardware issue...does anybody have suggestions for where on the motherboard I should start looking? Thanks.

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Do you have an AV adapter cable to check the optical digital audio output?


The audio comes from the MCPX chip and is sent to a WM9709 audio DAC to a low-pass filter to the AVIP port pins 2 Right Audio out and 4 Right Audio ground along with pins 3 Left Audio out and 5 Left Audio ground. LRMR3ut.png

Trace back the signal paths of these output signals to the Filter/Amplifier Coupling Network then back to the WM9709 Audio DAC.

Search for datasheets to determine each pin's function of each integrated circuit (IC) used along the audio output paths - left and right.

I'm assuming both channels are out, correct?  If so, a loss of the clock to load data from the MCPX's digital audio outputs into the audio DAC for conversion to analog audio will cease.


Edited by KaosEngineer

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Thank you for your reply, it is very helpful. Yes, both L and R analog channels have no output.

Great idea to try the digital output. -.I soldered in a coaxial cable to AVIP points 6 and 24 and it does have output sound over digital coaxial. I'm assuming this means the analog problem lies with the Filter/Amplifier Coupling Network, the WM9709, or the associated traces?

I have found the WM IC on the board but I'm still searching for the Filter/Amp.

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Trace the analog DAC outputs to the input of the filter/amp op-amp and/or the analog AVIP outputs back to the filter/amp output.

WM9709 pin 16 Line_Out_Left and pin 17 Line_out_Right.

Line_out_right gets to pin 3 and line_out_left to pin 5 of the op-amp after each passing through a capacitor and a couple of resistors.

The op-amp, an LM358 IC, used in the filter/amp outputs are pin 1 Right, pin 7 Left but there's more circuitry after the op-amp output to capacitively couple the audio outputs to the AVIP connector and possibly passes through some ESD protection.

Edited by KaosEngineer

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Board Life Status

Board startup date: April 23, 2017 12:45:48
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