TK.

Upcoming MBHP_MF_NG module

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Just as I was giving up hope, I got it to work.  I spent all last night reading every post I could find and in one post in another thread @Zam talks about the fader plate being to thin for grounding or something along those lines. Anyways, as I was ready to pack it all up and thought let me try one more thing. Everything I tried was grounding to the case which is about 1mm thick but every time I grounded anything to the chassis, nothing got better. So I thought let me try something thicker, as soon as I grounded it to the rack rails of my desk (rack rails are 3mm thick) ...Voila! the noise was gone. @Zam was right all along. 

On 6/23/2020 at 7:32 AM, Zam said:

You'll have to try to chassis ground fader metal part to minimize EMI leaking and motor sparkle.

As soon as I grounded the J14, the fader metal and the motor case everything was noise free. It was the temporary case I was using that wasn't sufficient to be used as a ground.

@Zamgave me the best advise (and I didn't listen) which was:

On 6/23/2020 at 0:50 PM, Zam said:

As a global rules, as it is for console integration, I'll suggest to build the thing as close as possible to final integration, to minimise bad surprise at the end as loosing time to fix issue that will not happen in the proper frame/mechanical integration.

So now I'm off to design my face plate and get it either in 3mm aluminum anodized or aluminium powder-coated. If anyone knows if there is going to an issue with either of these materials and grounding please let me know.

Thanks again @Zam for the help!

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Hello Zeke

Good you find solutions to your problem

It seem (I can be wrong) that you misunderstood  the concept of ground, the thickness of a case have noting to do with it, I suspect in your fist attempt you just connect together your Vref (0V here), fader can and metal case, without path to safety/earth ground, meaning everything stay floating. As soon as you connect all this to rack frame you create a path via rail and other equipments, I suggest your fader rack get it's own path to main ground to not interfere with other equipment (otherwise parasitic current might flow trough them)

technical note: powder coating as anodization (surface only) are non conductive !

for example you have to mask before coating or scratch surface after, if you want proper conduction between metal part in rack assembly.

Best

Zam

 

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@Zam Feels good to solve a problem, that's for sure. Especially since I am very new to all this. You are right though, I may have confused the concept of grounding. As an experiment, I will try later today to scratch the case I have because it might be the coating that was causing it not to ground properly. I'm using Front panel designer and the materials that I can use for making the face plate aluminum anodized or aluminium powder-coated. What if I used Aluminum Raw is that conductive enough?

I'm going to do more research on earth/ground but my understanding is grounding is done by going to a chassis and earth is going to..... well earth. My limited understanding is the way you earth is via the power receptacle but this board only has 2 holes, a negative and a positive. So I'll have to figure out how to earth it.

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Use the material you want for the visual finish you want ! row alu is ugly for front panel and easy to scratch...

I'm just saying this in the manner that you should anticipate your enclosure design and be sure all metal part have good electrical connection between them, a recessed screw or countersunk head screw that fix front panel to frame should be enough (as milling will remove the surface anodization )

"basically" your pcb 0V should be hooked at one (and only one) solid screw at the frame (common ground), preferably close to the main entry, where you also connect the safety earth ground from the (close) main connector.

In your particular usecase I think fader screw mount (countersunk) will do the job to connect fader metal can to common ground.

Your fader 0V audio should not share the fader box common ground, it's already connected at console rack module via trace, pcb and local chassis common ground.

Try to imagine the audio part of the fader as an isolated extension from outside the fader box.

Best
Zam

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