Middle Position Hum Cancelling P-90

[rgates]

I have a recently purchased an Epi Goldtop that I'm very happy with. The pups sound much better than I expected them to sound, however the middle position is not hum cancelling.

I know that my other P-90 guitar features this.

Can I reverse the leads of one pups to achieve this? Both pups have 2 conductors, one hot the other to ground along with an additional shield to ground. I'm thinking that I might just swap the leads on the neck pup but I don't want that out of phase sound either (I don't know if that only applies to humbuckers)



Thanks

Rick

 

[Artie]

Re: Middle Position Hum Cancelling P-90

Hey Rick; I'm pretty sure that if you swap any of the leads of any pup, its going to be out-of-phase with the others. I believe a P-90 is a single coil, which means, to make it hum-cancelling, it must have been designed that way. That is, reverse wound/reverse polarity. Reverse polarity here refering to the magnet, not the pup wires.

 

[rgates]

Re: Middle Position Hum Cancelling P-90

I've swapped magnets in HB's before, is it the same idea for a P-90? That way, I may be able to reverse the leads and flip the magnet. I've never had a P-90 open before.

Rick

 

[Artie]

Re: Middle Position Hum Cancelling P-90

I'm not sure about that. A hum-cancelling single would be both reverse-wound and reverse magnet polarity. Hopefully, someone else will jump in.

Also, I believe that P-90's may be potted in such a way to make disassembly difficult. Again, hopefully someone else can clear that up.

 

[Zhangliqun]

Re: Middle Position Hum Cancelling P-90

Hey Rick; I'm pretty sure that if you swap any of the leads of any pup, its going to be out-of-phase with the others. I believe a P-90 is a single coil, which means, to make it hum-cancelling, it must have been designed that way. That is, reverse wound/reverse polarity. Reverse polarity here refering to the magnet, not the pup wires.

P90 has two bar magnets instead of just one, with one pole of both magnets (say north) facing the polepieces and the other poles to the outside (south).

All you need to RWRP it to make it hum cancelling in the middle position with the other P90 is just flip the magnets and reverse the leads of one of the P90's.

 

[rgates]

Re: Middle Position Hum Cancelling P-90

So before I screw this up, do I flip the magnets away from the polepieces? The long edge facing the outside would now be facing the polepieces?

Thanks
Rick

 

[Artie]

Re: Middle Position Hum Cancelling P-90

Yeah, flip the reds for blues:

And, if you really mess up and drop it on the floor - no problem. Line the two magnets up so they oppose each other, and hold them to the pup in there original position. Then hold that pup over either of the others - pole piece to pole piece. If they attract, you have them flipped. If they repel, you have them back to stock.

 

[rgates]

Re: Middle Position Hum Cancelling P-90

Thanks for the info.
I took the pup out of the guitar enough to look at it (still soldered) and the magnets are definitely stuck. I loosened the mounting plate enough but I'm guessing the wax is holding them pretty tight. Hair Dryer?

Rick

 

[Artie]

Re: Middle Position Hum Cancelling P-90

At this point, I'm not sure. I've only flipped the mags in a humbucker before. Hopefully Zhang will stop back by. I think he's done it.

 

[rgates]

Re: Middle Position Hum Cancelling P-90

Done and Done!
Works perfectly, thanks!!!
Hair Dryer and an X-Acto No.11
21 minutes from finding the dryer to tested and re-assembled.

Any idea if the bars are the same size as a humbucker? I wish I measured them when I had them out.

Rick

 

[Zhangliqun]

Re: Middle Position Hum Cancelling P-90

Done and Done!
Works perfectly, thanks!!!
Hair Dryer and an X-Acto No.11
21 minutes from finding the dryer to tested and re-assembled.

Any idea if the bars are the same size as a humbucker? I wish I measured them when I had them out.

Rick

They should be the same size -- definitely the same width (1/2") and thickness (1/8") and only a slight variation on the length, if any, which doesn't really matter much.

 

[rgates]

Re: Middle Position Hum Cancelling P-90

Any idea where I can buy a couple sets of Alnico 2 & 4 mags for experimenting?

Rick

 

[Zhangliqun]

Re: Middle Position Hum Cancelling P-90

www.allstarmagnetics.com

But the minimum order is $75. On the bright side, this means you can get plenty of Alnico 2, 3, 4, 5, and even the mighty Alnico 8 and ceramics too so you can experiment with magnet swaps endlessly.

If you just want Alnico 4, Fralin will sell you some and I don't think he has a minimum order.