JMJM shielding and harness change project

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metsam
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JMJM shielding and harness change project

Post by metsam » Tue Jan 12, 2021 11:19 am

Hello everybody,

As I removed everything from the JMJM body, just before shielding it, I 've got a question.

https://i.imgur.com/ln0aKwm.jpg

As you can see in the picture, there is one cable coming from the bridge post, that was soldered on the back of the volume pot.

After I shileld all the cavities with copper tape (except the trem cavity), I will resolder it to the volume pot.

Tha question is, should I solder the copper tape itself to the volume pot with a second cable, or the shielding does not need to be grounded?

Thank you in advance for your time!

Cheers!

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Bradley-Jazz
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Re: JMJM shielding and harness change project

Post by Bradley-Jazz » Tue Jan 12, 2021 11:38 am

The shielding absolutely does need to be grounded, otherwise it can introduce more noise.

If you have an anodised pickguard and it is conductive from the underside (I’d check with a meter), then you can overlap the shielding at the top of the cavity in a convenient location so that the guard will screw down on to it and make contact. The guard will then make contact with the vol pot.

You could solder a wire on instead, but it can be trick to solder to foil. Another alternative would be to use a screw tag screwed through the foil, and connect the wire to that.
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Re: JMJM shielding and harness change project

Post by metsam » Tue Jan 12, 2021 12:09 pm

Bradley-Jazz wrote:
Tue Jan 12, 2021 11:38 am
The shielding absolutely does need to be grounded, otherwise it can introduce more noise.

If you have an anodised pickguard and it is conductive from the underside (I’d check with a meter), then you can overlap the shielding at the top of the cavity in a convenient location so that the guard will screw down on to it and make contact. The guard will then make contact with the vol pot.

You could solder a wire on instead, but it can be trick to solder to foil. Another alternative would be to use a screw tag screwed through the foil, and connect the wire to that.
Thanks for the answer! I will shield the pickguard also, it is not contactive itself, I measured it with a multimeter.
Also planning to overlap the Shielding at the top of cavities at several points.
This contact to the volume pot through the pickguard, is not ground, right?
I should be fine just like this, right?
Thanks again!

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Re: JMJM shielding and harness change project

Post by Bradley-Jazz » Tue Jan 12, 2021 2:02 pm

Hi, so you’re shielding the cavity you can make sure it connects well to the shield you add to the pickguard by wrapping it over the body top over one of the pickguard screw holes (but obviously not so it would be visible when the guard is in place). Make sure the shielding to the pickguard covers the corresponding hole in the guard, then when you screw the guard down, poking the screw through the foil, it will clamp the two bits of foil together securely.

Stick the shielding to the guard straight across the pot holes, then you can trim it neatly to the holes with a scalpel so that the pot body will contact it when you bolt them on. You can check the contact between the pickguard shield and the back of the pot with a multimeter, just to be sure. The back of that pot is then wired to ground, so you have grounded your shielding.

I hope that’s the info you are after!
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Re: JMJM shielding and harness change project

Post by andy_tchp » Tue Jan 12, 2021 3:15 pm

Is it an anodized guard? If so, it surely is conductive.

You need to knock/scrape the anodizing off for anything connecting mechanically to it for the purposes of grounding though.
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Re: JMJM shielding and harness change project

Post by Larry Mal » Tue Jan 12, 2021 4:29 pm

Often you see little rings of bare aluminum around where the pots go, that will ground that way.
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Re: JMJM shielding and harness change project

Post by metsam » Tue Jan 12, 2021 11:10 pm

andy_tchp wrote:
Tue Jan 12, 2021 3:15 pm
Is it an anodized guard? If so, it surely is conductive.

You need to knock/scrape the anodizing off for anything connecting mechanically to it for the purposes of grounding though.
Tested it last night, it wasn't conductive!

Unless if the bottom side is and the top is not, but I believe it's highly unlikely.

Thank you! :)
Last edited by metsam on Wed Jan 13, 2021 2:01 am, edited 1 time in total.

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Re: JMJM shielding and harness change project

Post by metsam » Tue Jan 12, 2021 11:12 pm

Bradley-Jazz wrote:
Tue Jan 12, 2021 2:02 pm
Hi, so you’re shielding the cavity you can make sure it connects well to the shield you add to the pickguard by wrapping it over the body top over one of the pickguard screw holes (but obviously not so it would be visible when the guard is in place). Make sure the shielding to the pickguard covers the corresponding hole in the guard, then when you screw the guard down, poking the screw through the foil, it will clamp the two bits of foil together securely.

Stick the shielding to the guard straight across the pot holes, then you can trim it neatly to the holes with a scalpel so that the pot body will contact it when you bolt them on. You can check the contact between the pickguard shield and the back of the pot with a multimeter, just to be sure. The back of that pot is then wired to ground, so you have grounded your shielding.

I hope that’s the info you are after!
Thanks again! :)

So the shielding needs grounding, and it does so through the pickguard shielding and the volume pot!

🤔 Right? :)

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Re: JMJM shielding and harness change project

Post by metsam » Tue Jan 12, 2021 11:13 pm

Larry Mal wrote:
Tue Jan 12, 2021 4:29 pm
Often you see little rings of bare aluminum around where the pots go, that will ground that way.
Yes, I know what you mean!

Thanks a lot! :)

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Re: JMJM shielding and harness change project

Post by Bradley-Jazz » Wed Jan 13, 2021 3:04 am

metsam wrote:
Tue Jan 12, 2021 11:12 pm
Bradley-Jazz wrote:
Tue Jan 12, 2021 2:02 pm
Hi, so you’re shielding the cavity you can make sure it connects well to the shield you add to the pickguard by wrapping it over the body top over one of the pickguard screw holes (but obviously not so it would be visible when the guard is in place). Make sure the shielding to the pickguard covers the corresponding hole in the guard, then when you screw the guard down, poking the screw through the foil, it will clamp the two bits of foil together securely.

Stick the shielding to the guard straight across the pot holes, then you can trim it neatly to the holes with a scalpel so that the pot body will contact it when you bolt them on. You can check the contact between the pickguard shield and the back of the pot with a multimeter, just to be sure. The back of that pot is then wired to ground, so you have grounded your shielding.

I hope that’s the info you are after!
Thanks again! :)

So the shielding needs grounding, and it does so through the pickguard shielding and the volume pot!

🤔 Right? :)
Yes, the shielding always needs grounding, and in the option discussed above, it makes electrical contact through the pickguard shield and pot.

It can be grounded any way you like (the route doesn't matter), but that option avoids soldering to foil (often problematic) or buying screw on tags for wiring.
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Re: JMJM shielding and harness change project

Post by andy_tchp » Wed Jan 13, 2021 3:18 am

metsam wrote:
Tue Jan 12, 2021 11:10 pm
andy_tchp wrote:
Tue Jan 12, 2021 3:15 pm
Is it an anodized guard? If so, it surely is conductive.

You need to knock/scrape the anodizing off for anything connecting mechanically to it for the purposes of grounding though.
Tested it last night, it wasn't conductive!

Unless if the bottom side is and the top is not, but I believe it's highly unlikely.

Thank you! :)
No.

Again - you need to remove the anodizing in spots requiring grounding through a mechanical connection (like the 'bare rings of aluminium' Larry mentioned), to get continuity.

It's aluminium. It's conductive. Absolutely zero point in adding additional shielding.
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