Wiring Questions / Help

[crull]

I'm hoping someone can help me out here with a few wiring questions.
I recently re-wired my Epiphone with (bridge) Custom 5 and (neck) 59. I installed all new CTS audio taper pots, .02 uf orange drops, and a three way switch.
I used a star grounding lug in the control cavity, and shielded all the compartments with copper tape. So everything pretty much has it's own ground line.

What I have noticed through testing is when the switch is in the treble or rhythm position. Some of the signal from the other pickup is still getting into the output. I can tell it is because when I touch the pole pieces with a small screwdriver I can it hear it unless I turn the volume control totally off on that pickup that is not being used. Is this normal?

At first I thought it was because I was using a two conductor shielded cable to the pots and some of the signal from the other pickup was being picked up in the cable run. So I switched each pickup to having it's own shielded cable, but it didn't make a difference. So somewhere the signal is bleeding into the output line even though its off at the switch. I measured at the switch and when a pickup is off there is still a high ohm reading to the center of the swtich for that pickup that should be totally off.

Any help would be greatly appreciated thanks.

 

[Artie]

Re: Wiring Questions / Help

I measured at the switch and when a pickup is off there is still a high ohm reading to the center of the swtich for that pickup that should be totally off.

Any help would be greatly appreciated thanks.

How are you making this measurement? If you don't disconnect the hot wire of the selected pup from the 3-way, you'll read through it. Also, you'll read through the volume control, which will be a much higher resistance than the pup itself.

I know its a pain in the butt, but what you need to do is, disconnect either the bridge or neck hot wire from the 3-way. Then put the 3-way in that position. (If you disconnect the neck, put the 3-way in the neck position.) Then measure from across the output jack. It should read "open", or infinite. If it doesn't, then we can go from there. That would mean something miswired somewhere.

 

[crull]

Re: Wiring Questions / Help

How are you making this measurement? If you don't disconnect the hot wire of the selected pup from the 3-way, you'll read through it. Also, you'll read through the volume control, which will be a much higher resistance than the pup itself.

I know its a pain in the butt, but what you need to do is, disconnect either the bridge or neck hot wire from the 3-way. Then put the 3-way in that position. (If you disconnect the neck, put the 3-way in the neck position.) Then measure from across the output jack. It should read "open", or infinite. If it doesn't, then we can go from there. That would mean something miswired somewhere.

Thanks for responding.

When I measure from the center of the switch to the selected switch terminal on the switch I get 0 Ohms. When I measure from the center to the other terminal that should be off I get around 21K Ohms. That's a high resistance, but why am I reading anything at all?

If that pickup is off why am I still reading a resistance to the center terminal? Shouldn't that pickup be totally out of the picture when the other pickup is selected?


I double checked all the connections. The braids are only grounded on one end. I honestly can't see how some of the pickup signal is getting into the output even when it is switched to the other pickup. It's not a lot of signal, but it's still there...the only way to get rid of it is to make sure the volume control is turned down for the pickup that is off.

When you switch to the treble pickup, does some of the signal from the Rhythm pickup still get into the output if it's volume control is not turned all the way down?

Thanks for the help.

 

[Artie]

Re: Wiring Questions / Help

If that pickup is off why am I still reading a resistance to the center terminal? Shouldn't that pickup be totally out of the picture when the other pickup is selected?

Not exactly. You're reading all the way back through the pup that is selected, to ground, and back through the pup that isn't selected. From point "A" to point "B", through the green line. Like this:

When you switch to the treble pickup, does some of the signal from the Rhythm pickup still get into the output if it's volume control is not turned all the way down?

Thanks for the help.

It shouldn't. There must be something amiss in the wiring. Its possible that you could get bleed-through if wires are close to each other, but I've just never heard of that happening.

I'll continue to think on this. Hopefully, someone like OctaveDoctor or Kent S may chime in.

Artie

 

[crull]

Re: Wiring Questions / Help

Thanks for that detailed drawing. It really helped a lot in visualizing whats going on. Now I can understand why I am still reading something on the other pickup thats off.

I still don't know why I am getting some of the signal in the output though when each pickup is off. None of the hot wires from each pickup are close to each other except for running through the body, but each has it's own shield. I'm wondering if it's possible for the hot wire to the output jack to pick up some of the output from the hot wires from the pickup that is off at the switch because I can't figure out why it's like it is.

I attached a picture of how I wired it together. The light gold color is the copper shield.

 

[Artie]

Re: Wiring Questions / Help

It looks like you did everything right. I assume those two big squares over the pups are the baseplates.

I have to kinda grasp-at-straws here, but there's a couple things Id try. Disconnect one of the hot wires from the switch. See if you still get bleed through. That will, at least, tell you that the problem is someplace else.

I have a mild suspicion that your problem is related to using all those shielded wires. The thing is, I hate to have you rip everything out if I'm wrong. If the shielded wire is cheap-ish - and by that, I mean the shielding isn't all that good of quality - it may have fairly high resistance in it. It will pick up the signal from the inner conductor and impress it on to ground. Then you'll get the symptom you have.

Like I said, I hate to have you rip everything out based on what I say, but if it was me, and this problem is really bothersome, I'd remove all the shielded wire and see what affect that has. But it may not help at all. Its a tough call.

Artie

btw - You may want to wait for others to chime in. I might be overlooking something. I'd really like OctaveDoctor to weigh in on this one.

 

[crull]

Re: Wiring Questions / Help

The squares above the pickups are the copper tape shields in each humbucker cavity. I ran a ground wire that connects to all the cavities and then to the center lug in the pot cavity. The pots are all grounded by the copper shield.

The wire I am using for the center of the switch to the output jack came with the epiphone. I'm not sure how good of a shield it is compared to other shielded wire, but I tend to agree that it could be the cause. I know the problem is happening after each pot, because when the pots are turned to 0 no more bleed through. So somewhere from the switch to the output jack the signal is getting into the output from each pickup when it is turned off.

It's not a major problem, but I would really like to know why it is happening. I did replace the switch wires to their own cable, and still the same thing. The only wire I think it can be is the output wire which I'm not sure if I want to replace just yet.

Thank you very much for your help.

 

[Artie]

Re: Wiring Questions / Help

I know the problem is happening after each pot, because when the pots are turned to 0 no more bleed through. So somewhere from the switch to the output jack the signal is getting into the output from each pickup when it is turned off.

You can't really make that assumption. The volume pot will ground that line, and kill the signal, regardless of whether the bleed-through is happening before or after the pot.

 

[crull]

Re: Wiring Questions / Help

Good point.

I was also basing that assumption on each pickup having it's stock shield to ground and the quality of the shield that comes with each pickup. I can't find anything wrong with the wiring else where. So like you stated I'm thinking it's the quality of the shield that is on the wire connected to the jack and the center of the switch. I already replaced the wires for the outside terminals on the switch with no difference....so that pretty much leaves the center wire which I haven't replaced yet. When I had the wires off the switch I tested it and it was OK. I also did another test with the amp on and the signal that is getting into the output is very low from the off pickup. I do know there is a slight input from the off pickup though by touching the pole pieces with a tiny screwdriver, but whether or not that is effecting the sound of the on pickup all that much I can't tell.