!!! Xmos Problem !!! Dual AK4495S AK4495SEQ AK4118 DAC decoder XMOS USB w/LME49990

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AIM65

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Joined 2015
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It's likely you've an issue with the negative supply.
Could you post a picture of the label on the transformer ? and measure, in AC, the voltage across the yellow and brown cable located on the opposite side of the green connector. (not the center one !)
 
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MykhailoM

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Joined 2012
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AIM65

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MykhailoM said:
Here is the picture of the transformer: Shared album - Mykhailo M - Google Photos and I will take the measurement in a moment

I`m not sure if I measured correctly. I placed the multimeter - one pin on the transformer Black pin and another pin on the opposite contacts. I got 0.3, 0.3 and 0.2, 0.2 on the brown and yellow. Shared album - Mykhailo M - Google Photos
Click to expand...

With the DMM in AC. Place one probe on the brown cable attached to the 3 screws connector then other probe of the DMM on the yellow cable also attached to the 3 screws connectors, you should either Close 0 either close 36V.
 
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MykhailoM

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Joined 2012
Hi Oleg, by inserting this way ( which is wrong) it works or at least allows the signal go through if I would insert it in the correct way the sound will be blocked on both channels. If I remove the op-amps ( both) the sound still goes on both channels even with NO op-amps in there - strange. something around op-amps is wrong.
 
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OlegSh

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Joined 2010
I would suggest to make close-up photos of the op-amp socket and its surrounding (top and bottom of the board). This may help to understand what goes wrong with the op-amps. The presence of audio output without the op-amps suggests that the DAC output works. Since the only active part between the DAC and the line output is op-amp then we should concentrate on troubleshooting this part of the circuit.
 
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OlegSh

Member
Joined 2010
OK, some observations:

1. The board came with single op-amps which excludes using duals.
2. Four resistors have dry joints or no solder at all. I would expect bad or no electrical connection there. You should definitely resolder those joints.
3. The op-amps are still inserted wrong way around.
 
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AIM65

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MykhailoM said:
If I place multimeter points on both sides of the 3 points connection (not the middle with both wires) for brown and yellow I get 02.8V Shared album - Mykhailo M - Google Photos
Click to expand...

OK, on the 3 screws connector you should swap the 2 brown cable or the 2 yellow in order to get correct full wave rectifier setup. But it shouldn't solve the supply issue, you now should check the stabilizer.
I'm currently in the train arriving at the station, I should find some time later the get back in the thread

rgds
 
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MykhailoM

Member
Joined 2012
2. I have left those resistors unsoldered just in case I will need to change them again (didn`t effect the sound or change anything from removing previous).
3. I removed resistors completely now - didn`t change the sound or volume output. If I was to insert them correctly I will have no sound as the sound will be blocked.
 
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