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Capacitor grounding
http://diyaudioprojects.com/Forum/viewtopic.php?f=10&t=6373
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Author:  brimley [ 27 Oct 2018, 14:50 ]
Post subject:  Capacitor grounding

I didn't get any replies to my post Request for help fixing Nobsound Class D amp :(

So I wonder if I can narrow down my questions on this solution I'm trying to implement:

"The two capacitors marked yellow should be disconnected from local ground and connected to the ground of preamp
or as marked on the photo to the ground of potentiometer."


Q1 - Does it matter which capacitor leg I ground?
Q2 - How do I disconnect from local ground (if on a board...)
Q3 - Where would I find the ground on a potentiometer?

Apologies for the Noob questions, I'm just trying to fix something...

Thanks
Steve

Author:  gofar99 [ 27 Oct 2018, 17:17 ]
Post subject:  Re: Capacitor grounding

Hi, Since I didn't see the other posting...what exactly are you trying to fix? Looking at the photo the way to undo a capacitor is to unsolder one lead and lift that end free from the PCB. Which end I can't tell from the photo as it is unclear which end is the one needing to be changed. Then I would use wire (about 20 gauge or so) and solder it to the freed ends of the capacitors and run it to the location you need to connect to. If you are good with tools ....I personally would probably use a Dremel and cut the trace where the capacitors are soldered into the board and attach a new wire from there. Being very sure that they are really disconnected as some pcbs have multiple levels and being really sure that you didn't cut something else out of the circuit at the same time.

Good listening
Bruce

Author:  brimley [ 28 Oct 2018, 10:03 ]
Post subject:  Re: Capacitor grounding

Thanks Bruce, I'm trying to fix a bluetooth noise issue. (Seems to be a design flaw and I'm trying to implement a suggested fix)
I got some replies to my other post so now I just need to figure out which lug on the pot I need to connect to.
I'm guessing the middle, but emphasis on the guessing!

Author:  Yungman [ 29 Oct 2018, 01:28 ]
Post subject:  Re: Capacitor grounding

brimley wrote:
Thanks Bruce, I'm trying to fix a bluetooth noise issue. (Seems to be a design flaw and I'm trying to implement a suggested fix)
I got some replies to my other post so now I just need to figure out which lug on the pot I need to connect to.
I'm guessing the middle, but emphasis on the guessing!


Like I said, the best is to try to make the seller pay for return shipping. But if you really want to fix it, you have to take it apart and take pictures of the back side of the pcb to know where the return of the pot. Once you do that, you void all warranty and return.

Author:  Cliffystones [ 27 Feb 2019, 17:55 ]
Post subject:  Re: Capacitor grounding

I just wanted to ad to this thread, as I have found a device that really reduces BT noise. I discovered that the "tweedling" noise actually feeds back through the source voltage supplying the BT module. A company named Mornsun makes a little chip that works well. The part number for the one I'm using is B505S-1W. My BT receiver operates on 5V, and they also make them for different voltages. I just put this in line between the supply and the module and it removed 90% of the noise. The datasheet states that you can also add LC filters before and/or after the chip to further reduce the noise so I'm going to tinker some more and see if the noise can be eliminated or reduced below a perceivable level.

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