Tone on Nextion LCD Dimming
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A relative and I have both purchased the uBitx boards and upgraded to the CED firmware with a Nextion diplay (he has a 3.5" enhanced and I have a 2.4" enhanced).? Both exhibit a tone when the LCD is dimmed below 92.? We have tried adding capacitors to the 5v line to the Nextion display, as well as on the 12v general supply.? Nothing seems to remove the tone.
Testing on the audio output at the high end of the volume control reveals aprox 300 hertz signal that goes away when fully dimmed or full bright.? I have tried probing the 5vdc line to the display, and cannot find any signal there.
The only thing that has worked so far has been to use a separate 5 vdc supply for the display.
Any thoughts on what could be causing the tone?? Our current guess is that the dimming is done by chopping the supply to the LED back light.? But if this were the cause the filtering on the supply line should at least reduce the sound.
?Seems like over kill to add another regulator to solve the tone issue.
Thanks for any suggestion that you might provide.
Evan AC9TU
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