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loos

P-90 wiring

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I’m hoping someone can help me out with an electrical problem. I have an aftermarket Tele style guitar with a stock Telecaster PU in the bridge and a P-90 in the neck. I’ve been playing it with a standard three way switch but was intrigued by the idea of using a four way switch for the additional tonal possibilities. So I set it up following a diagram but it didn’t work out as I remember so I went back to the three way switch and all was well.

I see now, looking at the wiring diagram that there is mention of having to remove the cover ground when using a stock Telecaster neck PU and grounding the cover separately. Of course the P-90 does not have a metal cover so I had just wired it using the two wires, white and black which emerged in the control cavity.

This time I decided to remove the P-90 from the body and look more closely at it and I’ve found that there appear to be three wires, one of which is soldered to the bronze plate at the bottom of the P-90 which also has soldered to it the black wire from the coil end. The white wire from the coil travels separately to the control cavity.

So I’m wondering if I ought, to make things work, to replace the ground wire attached to the brass plate with another ground wire to the cavity and run the black wire from the coil directly to the cavity.

Hopefully this isn’t too awfully poorly worded to make out. I’ll appreciate any advice concerning Tele four way switch wiring using a P-90 in the neck.

Loos

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3 hours ago, loos said:

So I’m wondering if I ought, to make things work, to replace the ground wire attached to the brass plate with another ground wire to the cavity and run the black wire from the coil directly to the cavity.

I think what you have to do is separate the shared connection from the pickup wire and brass plate, and run a separate wire from the brass backplate to the nearest grounding point inside the guitar. This replicates the requirement for disconnecting the chrome coverplate and grounding it separately on a stock Tele neck pickup for the 4-way switching you're looking at.

 

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I'd imagined that would be the solution but really don't like to cut wires on a gut feeling. Thanks for the feedback, (ho ho) it is good to have your response. I'll do the backplate ground and see how it works. I ought to have results soon and will post then.

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I disconnected where the coil end was grounded, put shrink tubing over the bare bit of wire, added a dedicated ground wire and this did not seem to do what I want, the other PU worked, the P-90 didn't. So I reversed the position of the leads on the switch end and although now the setup worked there was so very much hum it was unusable. Strangely when I touched the bridge the hum was worse. So when I get a bit of time again I'll try replacing the wires and try again. The joys of debugging, alive and well.

Loos

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I take it you're trying to do the common Tele 4-way switching mod (like this one).

The mod to the neck pickup should be the same whether it's a P90 or a stock Tele pickup with the chrome cover, ie if there is a connection between the cover/baseplate and one of the pickup wires, it must be separated and all three wires made out individually to their respective terminations as per the wiring diagram. It should even work if you don't bother wiring the baseplate of the P90 to ground, although you may have more hum.

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Although my ground wiring looked OK when I added an additional wire grounded to the common grounds on the back of the tone pot the hum went away. I'm still not getting the sound I wanted but now this project is going to have to wait for other projects to finish.

Thanks all for your replies, they have been both helpful and encouraging.

Loos

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