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Thread: WIRING HELP ON PARTIAL COIL CUT

  1. #1
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    Default WIRING HELP ON PARTIAL COIL CUT

    Despite having tinkered with and rewired many guitars for over a decade my knowledge of resistors is still very basic and I would welcome assistance in a wiring idea I am trying to put together for someone.

    Guitar is a mid range Washburn that came stock with a 59 in the neck and a custom custom in the bridge. Stock controls are 2 vol and 2 VCC controls which graduate pups between series and parallel wiring. All 4 pots are coming out and being replaced by CTS 500k push pulls with the usual 2 vol 2 tone arrangement, However owner has got used to not having tone controls so the neck tone control push pull will by pass both tones when up. He also wants to keep series /parallel options on both pups. No problem . My possible difficulty is with the final push pull which he wants to put both pups into partial coil cut. PRS and Ibanez have made this very fashionable of late. The idea is that this will occur only when the pups are in parallel mode so combo options will be full bridge humbucker in series with either parallel or partial cut neck or vice versa., plus of course the 3 single pup options.

    After a bit of head scratching and doodling I have an idea for the wiring which may work if it's possible to do the partial coil cut by grounding only the cut coil to be partially cut through the resistor.. To clarify what I mean see Figs1 and 2 below. Fig 1 is the usual way of doing partial coil cut but if Fig 2 also works so will my wiring idea. This ,in very simplified form is shown in Fig 3. Apologies for the poor quality of the drawings but I hope the idea is clear..Click image for larger version. 

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  2. #2
    Slutbucker Pimpologist ArtieToo's Avatar
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    Default Re: WIRING HELP ON PARTIAL COIL CUT

    First off, ignore your fig 2. You have a coil and resistor connected between ground and ground. It does nothing. Fig 1 is simply the spin-a-split using a fixed resistance instead of a variable pot. So then, mod your fig 3 like this:

    Click image for larger version. 

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    This way, PP2 truly does nothing in series mode, but will place the resistance in series with one coil when in parallel. I'd suggest using a trim-pot, (probably 500k or 1M), so that you can "tweak" the value of the "split" until you get it right where you want it. Then, if you want, you could measure the trim-pot setting and replace it with a fixed resistor. But if it was me, I'd leave the trim-pot in so that you can re-tweak at any time.

  3. #3
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    Default Re: WIRING HELP ON PARTIAL COIL CUT

    Artie, again many thanks for pointing me in the right direction, I think Fig 1 is how many people do partial coil split. PRS do it this way but then their pups are only 3 wire.I gather from what you say grounding only 1 coil thru a resistor as per my Fig 2 does nothing other than give a normal coil cut. Wiring the resistor in parallel with the coil is completely new to me as a way of getting partial coil cut. Re resistor values I was actually intending to use two 250k mini pots for the resistors as I seem to have quite a few spare ones accumulated over the years. I understand PRS use 8.8k ohms and the figure of 4,7k ohms has been recommended on this forum as a good value.

    My one observation of your suggested amended diagram however is that a crucial function has been lost.i.e. PP1 no longer gives the parallel option as when up the screw coil positive wire goes nowhere.

    See my suggested amendment below which I think solves the problem


    Click image for larger version. 

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    Last edited by Gstring; 09-21-2019 at 04:53 AM.

  4. #4
    Slutbucker Pimpologist ArtieToo's Avatar
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    Default Re: WIRING HELP ON PARTIAL COIL CUT

    I see what you're saying. The way I did it does "split" instead of "full" parallel. Your 2nd fig 3 is correct. Good catch.

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