I swear, one day I'll learn... ( 5 way rotary to McCarty switching)

[bishop2332]

So I take my Cu24 to my local repair guy with the prewired toggle switch assembly so that I can toggle my way through pickup changes instead of twist a knob.

Easypeasy, right?

Well, dude was/is perplexed by the wiring schematic. Thing is, I KNOW he can work on electronics. I've had him do work for me in the past. Granted, it was just putting in new pickups, but this is basically the same thing.

After two hours of him cursing the thing, adding wires, removing wires, soldering and resoldering on the pots, he finally gets the thing to work.

Temporarily at least.

Well, the system still works, but it just seems like the grounds are reversed somehow. More specifically, when I take my hands OFF of the guitar, its quiet as a church mouse. When I touch any of the metal on the guitar, you guessed it, humsville.


I know nothing of reading schematics. Cant really solder my way out of a wet paper bag. Wouldnt even begin to know what to look for to fix it.

But maybe one of you have come across this in the past?

I wont take it back to that guy to fix it and hate the idea of having to pay again to get it fixed. Well, its not the cash as much as having to wait for the work to get done.

Any suggestions on what to look for in this case?

[Jim Collins]

Are you using the same pickups, and merely converting the rotary switch to a toggle switch? If that is the case, your repair guy may not be familiar with the fact that PRS pickups found in rotary switch guitars feature a neck and bridge pickup with opposing magnetic polarity. McCarty wiring using these pickups is different from McCarty wiring using two pickups with the same magnetic polarity. (Stock McCarty guitars have a neck and bridge pickup with the same polarity.)

Here is the text of a post I made many times, quite some time ago. It contains instructions on how to convert rotary switching to McCarty switching using the existing pickups.


Converting a rotary switch to McCarty wiring, using the existing pickups.



There will be some body modification required. The shaft of the rotary switch is narrower than the shaft of the toggle (assuming a Switchcraft toggle, like PRS uses). Take great care with this, or have someone experienced in woodworking tools do it for you. It is very easy to chip the finish on the guitar, and you only have the knurled nut to hide any goofs.



McCarty wiring also features a push/pull tone pot, as opposed to the standard tone pot that rotary switch guitars use. The shaft of the push/pull pot is narrower than the shaft of the regular pot, which means there will be room to spare in the hole, when you mount the push/pull pot. It is possible to center the pot in the hole, and tighten the nut, but you might have better success if you get a small piece of surgical tubing to put around the shaft of the push/pull pot.



The wiring of the neck pickup will be a little different from the wiring of the bridge pickup. The two pickups have opposing magnetic polarity. For the bridge pickup, the idea is to “move the ground” by pushing or pulling the tone pot. For the neck pickup, the idea is to “move the hot” by pushing or pulling the tone pot.



Let’s start by defining our environment. The push/pull pot has a DPDT (double pole, double throw) switch on its back. This switch has six lugs. The pot underneath it has three lugs. Face the pot so that the shaft is pointing away from you, and all nine lugs are facing you – as if it were mounted in the guitar, and you were looking in the control cavity.



We will name the three tone pot lugs P1, P2, and P3, from left to right.



The DPDT lugs will be named S1, S2, S3, S4, S5, and S6, with S1 being the top lug on the left, and S3 being the bottom lug on the left (closest to the pot casing). Similarly, S4 will be on the top right, and S6 will be on the bottom right (closest to the pot casing).



The volume pot lugs will be named V1, V2, and V3, from left to right, with the lugs facing you, and the shaft pointed down, as if it were mounted in the guitar, and you were looking in the control cavity.



The toggle switch has five lugs, assuming you use the Switchcraft toggle that PRS uses. With the shaft pointed away from you, and the lugs pointing toward you, you’ll see three lugs on top, and two on the bottom. These will be names T1, T2, T3, T4, and T5, from top left to bottom right. (If you are using a different switch, the switch may not have the same lug arrangement. It may only have four lugs. The lugs T4 and T5 will be jumpered together, as if they were one lug.)



When you remove the rotary switch from the guitar, you’ll see a red lead going to lug V1. Disconnect this lead from the rotary switch, but leave it connected to the volume pot. We’ll use it. (After all, you aren’t changing volume pots.)

The volume pot will also have a wire running from its casing to the casing of the tone pot. Disconnect this wire from the tone pot, but leave it connected to the volume pot casing. We’ll use it, also.



Bridge pickup. Black lead goes to T3. Red lead goes to S6. White lead goes to S4. Braided shield goes to ground (volume pot casing).



Neck pickup. Black lead goes to ground (volume pot casing). Red lead goes to S3. White lead goes to S1. Braided shield goes to volume pot casing.



Run a lead from S2 to T1.



Run a lead from S5 to ground (volume pot casing).



Run a lead from T2 to ground (volume pot casing). Lug T2 is an obvious ground lug on the toggle switch. It will not be connected to any other lug on the switch, regardless of the toggle switch setting.



Connect the existing lead from V1 to T4 and T5. (T4 and T5 are the output lugs from the toggle. Some toggle switches may have only one output lug.)



Connect a lead from V1 to P3.



Connect a .022uF capacitor between P2 and the tone pot casing. The chances are that the capacitor that was on the old tone pot was clipped too short to reuse. Get a new one. They are cheap.



Connect the existing wire from the volume pot casing to the tone pot casing.



That should do it.