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Audio Buzzing

Rich
 

I'm at a bit of a loss in all honesty.??

Audio is buzzing like a nutter.? I've tried three different power supplies, but this is ALL I get through the speaker, headphones, clansman's handset... doesn't matter what I try, nothing changes it.

Ideas?

Cheers

Rich
P7PEX

uBITX interference.mp3
uBITX interference.mp3

 

Disconnect antenna and see if it is coming in there and next try it on battery power.
--
Lee - N9LO? "I Void Warranties"

?
 

Hi Rich,
sounds like Nextion display with down regulated brightness. Do you use CEC-software with Nextion display?

73
DF1EA
Chris!
Rich aka M7PEZ
 

Right... in the audio, there's a humming and a clicking.? They're two sounds.??

I do indeed have a Nextion screen with CEC Chris.? Unplugging the screen does indeed remove the humming noise.

Let's see if a battery eliminates the clicking.
WA6PXC Rich
 

Hi Rich,
I have also had a buzzing noise in my audio.
I use a Nextion 5" screen. It was powered from the common LM 7805 5 volt supply
which is mounted to the radio chassis for a heat sink. I substituted an isolated 5 v supply
and the buzzing went away! To solve the problem, I placed a 1 watt 4.7 ohm resistor between the
13.8 volt supply and the input to the 7805, then placed a 470 uf 25 volt cap from the junction
of the 4.7 ohm resistor and the 7805 input to ground..Not a hint of buzzing now!

Kind Regards..
Rich WA6PXC

-----Original Message-----
From: Rich aka M7PEZ
Sent: Jan 27, 2019 9:27 AM
To: [email protected]
Subject: Re: [BITX20] Audio Buzzing

Right... in the audio, there's a humming and a clicking.? They're two sounds.??

I do indeed have a Nextion screen with CEC Chris.? Unplugging the screen does indeed remove the humming noise.

Let's see if a battery eliminates the clicking.

 

Perhaps a bigger reservoir cap to the screen supply? Or maybe even an active filter (emitter-follower)?

73 de ZL2DEX
 

Its from the display/MPU subsystem and likely due to power issue or ground loop.

Allison
Mike Short
 

Allison,

I am building a bitx40 for a ham in the metal case from India. What would be the best way to ground everything?

I put a ground lug on the front corner of the board, and ground off the paint around the antenna, PCB mounting points, display, etc.?
The grounds for the controls go to the lug. The antenna connection is about 2¡± long. Would there be any benefit to using coax?

I am putting PowerPoles for DC input instead of the barrel connector, and will ground the negative to the case.

Mike
AI4NS?
 

The case should be ground connect to it.? ?The best way is with a screw and a star washer.
Star washers will even pierce the paint but better to scrape it off.
The board mounting holes are ground use metal spacers to the case.
In all cases any paint on the inside needed to be removed to make a good connection.

I'd have built first with Raduino and verified working then stepped to the enhanced panel.

Use twisted pair for such a short hop to the antenna connector.

I prefer powerpole over those barrel connectors.? Only preference.

the power path to the enhanced board need to have a good ground the same as the
main board.

One last thing if the code is messed up it could be injecting the tone/buzz into the radio.

Allison
Mike Short
 

Thanks Allison. Those steps are what I am doing. Radio works fine. I test after each mod. So far, so good.?

You are a great resource.
N7XG
 

I am also having the same buzzing as described. I am using the uBitx with a 5" nexion screen, the base package including the audio amp. I have tried 2 different power supplies for the touch screen, same hum on both.

The hum is constant, that is always at the same level regardless of the volume control.
 

N7XG, Try to increase the brightness of Nextion display to 100% and check. I hope that helps.

Anthony
VU3JVX
N7XG
 

Can you give me some information how to adjust brightness?
 

N7XG,

If you have loaded the CEC Nextion display screen. It should be under "Home" -> "LCD Setting". Screen picture of your Nextion display will be helpful. As I have a 3.5' screen and the menu layout is bit different for 5' & 7' display.

Anthony
VU3JVX
N7XG
 

Anthony,

It is at 100%. When I lower it it gets real loud.
 

Dean (N7XG),

So you are able to find the root cause. I had the same issue with my 3.5 Nextion display, after making it 100% it went off. Yes it's gets worst if I try to reduce the brightness. However, I was sure this was discuss on this forum previously. I found the post?/g/BITX20/topic/67125540#73406

Good read about Nextion display @?

73 and Merry Christmas !!!
Anthony
VU3JVX

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