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ubitx receive audio troubleshooting

radiodoc43 All Messages By This Member #41162 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
Gordon Gibby #41173 开云体育 Where do you have a TPA 2016 chip? The uBitx does not use that. On Feb 4, 2018, at 11:12, radiodoc43 <Monsen.Craig@...> wrote: toggle quoted message Show quoted text 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
radiodoc43 All Messages By This Member #41174 My mistake. I meant TDA2822 chip. Craig KC2LFI
Gordon Gibby #41177 开云体育 So in order to have an oscillation, you have to have a closed loop with a gain greater than one at the oscillation frequency Since your squeal begins when you turn the vine control up, and then input of the loop that Apparently exists is earlier in the system. ? My guess would be via the power supply lines. ?That would suggest adding additional filtering in Decoupling capacitance in parallel with the lowest inductance (short leads ) as possible as near to the chips involved as possible. ? Probably the audio Amp chip & its preamp should have additional filtering on the power supply lines. ?You can test this by ?merely touching capacitance to the proper places temporarily. On Feb 4, 2018, at 13:21, radiodoc43 <Monsen.Craig@...> wrote: toggle quoted message Show quoted text My mistake. I meant TDA2822 chip. Craig KC2LFI
Mike Lichtman #41193 Craig, Just to eliminate audio vibration feedback (microphonics), disconnect an internal speaker and try and external one a short distance away from the circuit board and mic. 73 Mike KF6KXG
Nigel G4ZAL #41194 If using an external speaker, make sure it has a stereo plug (not a mono one). I mistakenly plugged a mono plug external speaker in and it squealed.

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