Defective TPA3116 with bluetooth

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Hi!

I've used the TPA3116 amps bought on ebay for some time and enjoy them, so when my sister needed an amplifier with bluetooth my choice fell on this one:

Finished TPA3116 Digital Amplifier Bluetooth 4 0 50W 50W Standard Version SN | eBay

It arrived in an undamaged package and looks fine.

Today I connected the amplifier to speakers and a 19 V, 65 W power supply to test it with bluetooth. It clicks 2 times when I connect the power supply and when I turn the amplifier on there is significant white noise in the left speaker. Right speaker is silent. When I press play on my phone (connected with bluetooth) it clicks again and starts playing music. The white noise in left speaker gets a little louder and the right speaker starts making strange noises (crackling). I ve tested with another power supply (125 W) that is adjustable between 15 and 22 V, no difference. There is no crackling in right channel when using the RCA input.

I opened it to see if there are any obvious errors and took these photos:

saDMjnd.jpg


1cIimjy.jpg



Sorry for not using the attachment function, the pictures would be so small that no details could be seen.

Can anyone see anything that is obviously faulty? The only thing I can see that is odd is two holes on the bottom edge of the bottom side (slightly to the right) that aren't filled with solder. Is that intentional?

/Anton
 
Flexing the PCB has no effect.

I did however notice something else. The noise increases substantially when I touch the potentiometer knob (if the volume is more than ~20 %). And the noise characteristic changes with volume, from purely white noise (at 0 %) to a more crackling (100 %).

/Anton
 
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