P-Rails wiring help?

[FriendlyUncle]

Hi! New guy here: a friend of mine came to me with plans to wire up a P-Rail in the neck and Burstbucker in the bridge of his Epiphone Les Paul. Problem is I've never worked with a P-Rail before and he wants to get the full spectrum of single coil sounds out of it. Even though it's an Epi, I don't want to drill the top for mini switches.

How should I wire the P-Rail in the neck to get humbucker, single coil blade and P-90 tones from it using two A500k push-pull pots in the neck volume and neck tone position? All the schematics I've found online assume the user is wiring up two P-Rails and show the push-pull pots sharing switching duties, which leads to my confusion as to where the Burstbucker would fit. I'm not new to installing pickups but I still find a degree of difficulty in troubleshooting wiring, especially where coil-tapping is concerned.

Thanks everyone! :bowdown:

 

[scarr]

Re: P-Rails wiring help?

You can use this diagram, but only wire up half of each DPDT (for all 4 variations). Note that it's the "inside" or "outside" of the switches being used for a single pickup.:
http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=2_prails_2v_2t_tspp

If you only want series humbucker, P90, and rail (no parallel HB), you can use this option. The "neck volume" would stay the same, but the "bridge volume" would only use half of the DPDT for a single pickup:
http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=2_prails_2v_2t_3w_2pp

Obviously, the switches can be relocated to whichever pots you like.

 

[FriendlyUncle]

Re: P-Rails wiring help?

Thanks Scarr. Now my buddy needs to order the push-pull switches. :smack: He already bought all the pickups but I had to make him aware to the fact that the P-Rail requires some sort of switching to access the other taps, be it through the Triple Shot, 3DPT switches or push-pull. We agreed that push-pull pots would be the cheapest route while remaining discreet.

I figure everything will be on my bench by next week. I'm feeling pretty confident if all need to do is remove the bridge pickup from the equation when reading the schematics. I figured that may work but wasn't 100%.

Thanks again!

 

[FriendlyUncle]

Re: P-Rails wiring help?

Alright, it took a little longer than expected but I have the guitar and pickups right now. I'm having trouble understanding the wiring diagram. I'll never get used to coil tapping!! :banghead:

Sooooo, as I stated earlier, ideally I'd like to keep the coil tapping push-pull switches for the P-Rail on the top row of the Les Paul's control layout to allow for easy switching...one in the neck volume for the single coil and the other in the neck tone position for the P-90 options. The Burstbucker in the bridge will assume the bridge V/T positions, as usual.

If anybody can whip up a diagram for me or break it down for me I'd greatly appreciate it. Thank you.

 

[hermetico]

Re: P-Rails wiring help?

Here you are the diagram:

and, here, the entry to my blog for further explanations:

http://hermeticoguitar.blogspot.com.es/2012/11/wiring-diagram-lp-1-prail-4-sounds.html

 

[FriendlyUncle]

Re: P-Rails wiring help?

Besos!! Thank you so much hermetico! My friend is in for an early Christmas gift.

 

[GuitarDoc]

Re: P-Rails wiring help?

Just a slight technical correction (semantics)...it's "coil splitting" not "coil tapping".

 

[FriendlyUncle]

Re: P-Rails wiring help?

Thanks GuitarDoc. I'm looking to split these coils UP! However...

Hermetico,

I wired up the P-Rail using the schematic you provided. It's buzzing like mad. Touching the metal, the actual pickups or their pickup screws has the opposite effect. It seems like every other P-Rail schematic I've seen has the green and bare wire soldered to the back of a pot with other grounding wires. I gave that a shot, as well as leaving the green wire soldered to a leg while soldering the bare wire to the side of the push-pull pot and neither setup produced ANY sound from the P-Rail.

HELP! :eyecrazy:

 

[FriendlyUncle]

Re: P-Rails wiring help?

I'm really bummed and my back hurts from hunching over the damn thing. Hazard of the job I guess. I'm thinking it may be a cold solder joint somewhere? All the joints look nice & shiny...

At first everything seemed to work, except the splitting portion was reversed to what the diagram says i.e. Neck Volume up = single coil and Neck Tone = P-90. Would that hint towards anything?

The push-pull pots react the worst when touched so no question it's definitely something going on with the P-Rail.

 

[FriendlyUncle]

Re: P-Rails wiring help?

Evening bump!! :banghead:

 

[hermetico]

Re: P-Rails wiring help?

Thanks GuitarDoc. I'm looking to split these coils UP! However...

Hermetico,

I wired up the P-Rail using the schematic you provided. It's buzzing like mad. Touching the metal, the actual pickups or their pickup screws has the opposite effect. It seems like every other P-Rail schematic I've seen has the green and bare wire soldered to the back of a pot with other grounding wires. I gave that a shot, as well as leaving the green wire soldered to a leg while soldering the bare wire to the side of the push-pull pot and neither setup produced ANY sound from the P-Rail.

HELP! :eyecrazy:

In my diagrams I am avoiding ground loops but, if your electronics cavity isn't shielded, you should throw jumpers from one pot's case to the other, then to the other, to put all them into the ground's network. Don't let any of those new ground jumpers to land twice in a pot's case.

About the pull/push going reversal. Maybe you missunderstood the diagram (what is shown far from lugs is "bottom" and, it depends on how the pot is placed) or maybe you have a reverse working pull/push (when it's up lower contacts are linked and, when it's down upper contacts are linked). But, I guess you got rid off that simple issue.

 

[hermetico]

Re: P-Rails wiring help?

Review your soldering work. It seems as you positivized the ground. Maybe some peeled signal wire can accidentally toch a ground. Are your capacitor legs isolated?.
Is any strand free?. Look at carefully your soldering work and, if it doubts, redo it again (I know it's weird but... sometimes is the best solution), carefully tracking every wire and soldering spot.
Take into account first what I've explained about pot case ground wires.

 

[FriendlyUncle]

Re: P-Rails wiring help?

In my diagrams I am avoiding ground loops but, if your electronics cavity isn't shielded, you should throw jumpers from one pot's case to the other, then to the other, to put all them into the ground's network. Don't let any of those new ground jumpers to land twice in a pot's case.

About the pull/push going reversal. Maybe you missunderstood the diagram (what is shown far from lugs is "bottom" and, it depends on how the pot is placed) or maybe you have a reverse working pull/push (when it's up lower contacts are linked and, when it's down upper contacts are linked). But, I guess you got rid off that simple issue.

Both push-pull pots brought to me were different brands, different lengths and one was slightly bigger than the other, requiring a tiny bit of reaming....so yes, it's possible they have different functions. I'll look into that possibility.

The cavity isn't shielded. It's a bog standard, late early 00's Les Paul.

I ended up running ground wires across all the pots, leading to the output jack, and the ground is no longer reversed. The new issue is that while the Burstbucker in the bridge is COMPLETELY silent when idle, the P-Rail still has a bit of hum behind the signal even when the strings are touched and both coils are active.

The parallel switching option does not activate either. Possibly more evidence to a reversed push-pull pot?

I'm going to double check the wiring as you've advised. I discovered last night that I had forgot to snip the bare end of one wire I soldered and it was resting firmly against the next leg over. Everything looked good to me but it's possible I got the red positive started on the wrong side of the push-pull box and need to do a little cleaning.

So here's the checklist:

Single Coil Rail Works
P-90 Works
Series Humbucker Works

Parallel Humbucker Option Doesn't Work
Persistent Hum in Middle and Neck Position

Any further help or input is appreciated. Thanks again Hermetico.

 

[FriendlyUncle]

Re: P-Rails wiring help?

Success!! The positive wire on the outside leg of the volume pot leading to the tone pot needed to be resoldered. It's always the small things.

She's acceptably quiet now in all positions and the parallel switching options works great. I think my buddy can live with the single coil and P-90 switching being the way it is. He never expressed a preference anyhow. Thank you for the schematic and all your help, Hermetico. And let me tell ya, this thing sounds great -- makes me want a set of P-Rails myself. Cheers Seymour!

 

[hermetico]

Re: P-Rails wiring help?

I am glad to hear you were able to get rid off the issues.
It's better to review three times every wire while soldering than to hunt ghosts later.
As we say here, "go you slow because I am in a hurry".