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Something's Not Quite Right In My Wiring


govtmule

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I have a tele style gutar wired up with two P-90's and a master volume.

I shielded the control cavity with copper shielding tape. The top 1/4" or so of the cavity has no shielding to make room for the cavity cover.

Here is a ROUGH diagram of my wiring:

wiring.jpg

The PUP's have the old braided hookup wire so as a ground I wrapped a wire around it two or three times and ran the other end to the volume pot case. See connections "A" and "B" in the above diagram.

The problem that I have is that if connections "A" or "B" are pushed down into the cavity the entire signal goes to ground. No sound at all from either PUP, no matter which one(s) are switched on at the time. If the connections are left alone, kind of hovering up about where there is no shielding tape the guitar plays just fine.

If I touch the tape I get a little more of a buzz through the amp.

The shielding tape is not grounded to anything directly but the volume pot is touching the tape directly because the mounting hole for the pot is taped as well.

If I run a ground wire from the shielding tape to the back of the volume pot, no sound whatsoever, all signal is grounded.

This is the first time I've shielded my electronics cavity so maybe I missed something, any help out there ?

Thanks,

Steve

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There are a bunch of problems with this wiring diagram...and a few of the procedures. A little late for me tonight to explain it all and more in my typical problem. In the meantime...it may be that you have wired the jack back to front...easy to do...so if you could check that or reverse this and see what happens that might help (although it may not be the explanation...checking the ground to hot with a multimeter is a better way).

The other problems relate to the switching...this is a very noisy implementation of lifting the pickup instead of shorting them, and you have the switching power...but it means a complete rewire of them...but I'll be back later...

pete

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There are a bunch of problems with this wiring diagram...and a few of the procedures. A little late for me tonight to explain it all and more in my typical problem. In the meantime...it may be that you have wired the jack back to front...easy to do...so if you could check that or reverse this and see what happens that might help (although it may not be the explanation...checking the ground to hot with a multimeter is a better way).

The other problems relate to the switching...this is a very noisy implementation of lifting the pickup instead of shorting them, and you have the switching power...but it means a complete rewire of them...but I'll be back later...

pete

Any help would be much appreciated Pete.

I did try and swap the jack wiring and got no sound at all after that so I must have at least the jack wired correct. :D

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If I run a ground wire from the shielding tape to the back of the volume pot, no sound whatsoever, all signal is grounded.

Sounds like the shielding is connecting to hot some how, a multimeter connected from the hot jack to the shielding would help to see that. Likely this is being connected when you squeeze everything back in. Pics might help.

For the switching, you have "lifted" the pickups (disconnected the hot) but a better way would be to have the pickups when off shorted to ground. This means changing your switching about so the pickup goes to the middle connection, the hot off one side, and the ground to the other.

Tele's can be a challenge, I chose not to shield the cavity on mine as there wasn't a lot of benefit and a lot of potential problems.

With bare shielding cable as on some vintage pickups (like my FWRHB) I solder a wire to the shield and then cover it all up with PVC tape so it can't short on anything. It may well be worth covering the internal shielding with such tape to stop electrical connection with wires or switch contacts when pushing things into the cavity.

But it's very tricky to know what is going on or how this is going together (such as if it is a typical tele cavity with a metal top control cover)...

pete

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Sounds like the shielding is connecting to hot some how, a multimeter connected from the hot jack to the shielding would help to see that. Likely this is being connected when you squeeze everything back in. Pics might help.

I figured this part out last night. The shieding was actually coming into contact with the PUP braided shielding cable when I tucked the wires back into the cavity. I cut away some of the shielding tape from around the hole that the PUP wire comes through and this corrected the problem. I'm guessing that this contact was creating a ground loop, correct ?

For the switching, you have "lifted" the pickups (disconnected the hot) but a better way would be to have the pickups when off shorted to ground. This means changing your switching about so the pickup goes to the middle connection, the hot off one side, and the ground to the other.

Sorry for the confusion.....I screwed up my little diagram. I actually already do have the PUP going to the middle and the hot off of one side to the pot. I am however, missing the ground coming off of the other side but it seems to be working fine without it.

With bare shielding cable as on some vintage pickups (like my FWRHB) I solder a wire to the shield and then cover it all up with PVC tape so it can't short on anything. It may well be worth covering the internal shielding with such tape to stop electrical connection with wires or switch contacts when pushing things into the cavity.

I was worried about that too so I tried to cover all of the exposed shielding cable with heat shrink tubing. The only parts left exposed were right where the wires came into the cavity....which is where the short, or ground loop, or whatever was occuring.

Thanks a lot for your help Pete. I'll add the ground wire from the switches and I think it should be good to go then.

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Well...if it works... :D

Seems like something wrong though...for instance, if the shielded braid is touching the shielded cavity (which should also be ground) this shouldn't cause a short and thus a loss of sound. A ground loop "may" introduce noise, but certainly not a short. If things are around the wrong way the ground wire to short the pickups (adding that wire) may introduce problems.

pete

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