Issues after shielding

[jonty1512]

Hi there 

 

I've recently tried shielding the control cavity of my Dean Edge 2 bass using copper tape and now all I get from the bass is a horrendous loud buzzing sound which gets even louder when I touch the strings. I have checked all of my wiring and all seems ok there, I have checked the copper throughout the cavity for continuity and that is ok as well. 

 

Prior to starting to shielding the cavity all was working well with the only issue being a hum which is why I wanted to shield the cavity in the first place.

 

Any help in solving this issue would be greatly appreciated

 

John

 

[mybass]

I would hazard that there has to be a contact with a ‘live’ wire somewhere, maybe at the jack point….maybe take all the shielding out and see if all is well, then try to shield the cover only and earth it and test.

[ikay]

It sounds like a grounding issue. Have you checked that the shielding itself is connected to a ground wire (ie. a wire that ultimately connects to the ground terminal of the jack socket)?

[Baloney Balderdash]

What you describe is exactly what happens when the hot wire/circuit is touching the ground/shield somewhere.

 

Look again.

 

Edited July 31, 2024 by Baloney Balderdash

[bremen]

Sounds like the copper is connected to the wrong end of the jack

[jonty1512]

Hi there

 

Thank you all for your advice regarding my shielding problem. What I have done is removed all of the copper tape I had installed as I could not locate the short circuit. At least the bass is now working again.

I've decided I'm going to take the nuclear option & completely upgrade all of the cavity wiring along with the pots & caps as the existing wiring is really thin and nasty and before I install the new wiring I'm going to paint the cavity with shielding paint.

 

Again thanks for all of your advice

 

John

[ezbass]

Insulating tape over the shielding, it’s what I had to do with my P, because the cavity was so tight, there was very little tolerance for any components that had twisted.

[prowla]

It could be one of the tabs on the jack socket touching the foil.

Perhaps only when you plug a jack in?

[bremen]

Thicker wire won't do anything. And ignore any advice about "star" grounding, it's only a thing when there's more than one current flowing eg in an amplifier. So long as the grounds are continuous, and theres no floating metalwork (pot bodies, knobs) youre good.

Insulating over the copper is often necessary as tabs on the socket move around as you plug in and can short out. But not in your case; if the tip was shorting to ground there'd be no signal. Anyway, good luck with the paint. Be sure it connects to the sleeve of the socket, not the tip!

[Obrienp]

Never a bad thing to replace cheap and nasty pots and wiring with decent quality parts but as has been mentioned, this won’t stop the hum. What you had, as commented by several above, is a live component in contact with your shielding. I have taken to always putting insulating tape over any shielding that could conceivably contact the pot tabs, cap, etc. it’s a really cheap fix and a lot less expensive than what you suggested.

[basstone]

As already noted, it's quite likely that a pot connection has made an unintentional contact with the screening foil. I always put an insulating layer of clear plastic sheet between the foil  screen and the pots to avoid the possibility of this happening. Screening foil is far more effective than conductive paint in my experience and well worth another go.

[bremen]

If the pot or jack had rotated and accidentally made contact with a correctly wired shield, as often happens in a tight cavity without insulation, the signal would be cut out.

 

OP reports a 'orrible 'um. 99% certain he's wired the shield to the wrong end of the pot.