ubitx receive audio troubleshooting

radiodoc43
 

I am still trying to identify the cause of an audio "squeal" which makes receiver unusable.

Audio is ok at lowest volume setting. As I turn up volume, a "squeal" begins and gets louder obliterating any other signals. The TPA2016 chip gets extremely hot if left in this state for any length of time. I suspect that something is causing the audio stage to oscillate at higher volume levels.

I have tried "cleaner" power supplies, created a ground plane for my front panel, and substituted shielded cable for the volume control leads, all without any improvement.

Any suggestions as to getting to the bottom of this problem?

Btw, the radio is able to receive strong signals at the lowest setting.

Craig
KC2LFI

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