P-Rail weirdness

[CrackedPepper]

Hello all - I know that some of you have P-Rails and I am looking to you for some feedback and, perhaps, an answer.  I am experiencing some weirdness with this configuration: http://www.seymourduncan.com/wp-content/uploads/2015/05/2PRail_3G_1VppSPL_1TppSPL.jpg

My wiring seems fine with regard to the functioning of the three-way selector and the pickups when both push pulls are in the up position or both are in the down position.

The diagram indicates that the corresponding coils should be completely off when the push/pull is down and the other is up. To me, that means that I should not hear any sound at all when I touch the screwdriver to the off coil just like I don't hear anything when the three-way is selected to the bridge pick up and I tap on either of the coils in the neck pick up and vice versa.

The weirdest comes in when either the P90 coils are selected or the rail coils are selected. In either case, the other coil should be shut off but when I tap on the shut off coil with the tip of the screwdriver I am still hearing a click. Is this normal?

Thanks in advance for taking the time to reply to this post. Happy New Year!

 

[stratamania]

The link you added seems to be incorrect.

 

[CrackedPepper]

Thanks stratamania - msg preview truncated the link but I fixed it

 

[Fat Pete]

Is the click just the same as when the coil in question is on, or is it a lot quieter? If it's quieter I'd guess it's just microphonic - the other coil is right next door and physically attached to the same baseplate after all. You may have to string it up and listen to be sure.

if it is the same volume then something's probably wrong.

Excuse me, stratamania!  :icon_biggrin:

 

[CrackedPepper]

Pete, it's definitely quieter but I don't think it's micro-phonic.  I'm using a really light touch. 

I posted the same message in the Seymour Duncan forum and got a response back:

P-Rail polepieces seem to respond to the screwdriver tap test, regardless of which coil is selected.

Can any of the builders here that used P-Rails confirm this?

 

[Cagey]

This is why I use a small tuning fork to test coil wiring rather than tapping on pole pieces. It's a non-contact way of exciting the coils, so there's no electrical or mechanical crosstalk.

 

[line6man]

Yeah, you are probably getting some crosstalk when you tap the pole pieces. That's normal.

 

[CrackedPepper]

Thanks guys!

Cagey - how do you use the tuning fork to test one coil vs the other?  If the wiring is correct, I can see how that will work.  This is probably a dumb question but if my wiring wrong and they are both active when only one coil should be, how will I be able to tell?

 

[Cagey]

If you hold the tuning fork right, the effect of the thing is very localized. I hold it lengthwise along the pickup, with the fork tangs perpendicular to the coil(s). Move it from one coil to the other, if there are two. That'll tell you which coil is hot or not, or both. You can also check your volume and tone controls, as well as your switch(es) while you're at it.

If the wiring is wrong, you'll have to suss that out on your own based on the responses you do or don't get.

Edit: resist the urge to bang the fork on your guitar's body. It won't do the body any good at all  :icon_biggrin:

 

[CrackedPepper]

Edit: resist the urge to bang the fork on your guitar's body. It won't do the body any good at all  :icon_biggrin:

I thought that was purpose of the guitar horn...

Thanks Cagey!

 

[Ace Flibble]

I think it's worth highlighting that this is extra common for P-Rails because of how they are designed. The smaller coil is very, very close to the large coil, and of course they're not even on separate bobbins. They're more like a tapped P-90 than a normal humbucker. So hitting them to test signal is pretty useless with P-Rails.