Control cavity shielding?

[rspst14]

Hey guys, this may sound kind of silly, but can copper shielding tape actually cause grounding problems? I rewired my entire guitar, and I had a humming problem with low output unless I was touching something metal on the guitar. I resoldered all the connections, and it still hummed no matter what I did. This is a very basic wiring layout, 2 humbuckers, 1 volume, 1 tone, 3 way switch. No fancy wiring tricks. I checked and rechecked, soldered and resoldered. This is the cleanest wiring job I've ever done, and everything was connected properly. The only thing different from before was the copper shielding foil I got at GuitarElectronics.com. The whole point of shielding tape is to prevent electrical interference, it couldn't be the cause of my humming problems, could it?

Ryan

[rspst14]

Re: Control cavity shielding?

http://www.harmony-central.com/Guitar/Faqs/faq/faq.shielding.txt

Okay, if I'm reading this properly, all I had to do was solder a wire from the shileding foil to ground????

I guess you learn something everyday.

Ryan

[John Wymore]

Re: Control cavity shielding?

I am amazed how often this step gets left out :-)

The shielding does no good unless it has a zero resistance path to ground. Remember, if you use multiple pieces of foil you need to put a little solder joint between each piece to create good conductivity.

When I do a shield job I check several points over the entire cavity to make sure I have a 0 ohm continuity everywhere. If you shield pickup cavities like in the attached picture link you need to run a wire from the pickup cavity to the main cavity.

Here's a pic of a Jazz basscavity I did last week ...

http://a3.cpimg.com/image/B9/2F/33316793-5c80-02000180-.jpg

[rspst14]

Re: Control cavity shielding?

So what you're saying is that I should have used one large piece of shielding foil instead of a lot of small pieces...oops. Well, I'll certainly chalk this up as a learning experience. Looks like I'll need to redo this. I was ready to throw the guitar out the window after four hours of soldering and resoldering. If you use shielding paint instead of the foil, do you still need to solder a ground from the bottom of the cavity to the central ground point? I shielded the control pot cavity, the pickup switch cavity, and the pickup routes. Is it necessary to shield the control cavity covers too, and if so, do you also need to run a wire from the shielded cover to the ground point? Thanks.

Ryan

[John Wymore]

Re: Control cavity shielding?

Ryan,

It's OK to use multiple pieces, just put a tiny solder joint between each one so there is continuity between them. If you look closely at the picture in my previous post you will see some tiny little solder dots in there. That's all you need and it's easy to do.

When using paint you still need to get to ground somehow. You can't solder to the paint though so I usually wrap a wire around a small screw and screw it into the cavity before painting over it. BTW, I used to be a big fan of the paint but after doing some testing I find the foil does a much better job of shielding and is well worth the extra time it takes to do.

Yes, I always do the covers too and do the tape in such a way that the cover foil makes contact with the cavity foil to create a connnection.

Just remember ..... all the shielding must be 0 ohms or at most 5 ohms resistance back to ground and all will be fine.

[rspst14]

Re: Control cavity shielding?

Great, thanks for the help John.

Ryan