Mcarty wiring question

Yzerman

New Member
Joined
Feb 5, 2016
Messages
35
Hi,

I just bought a used 2000 Mcarty with a Duncan bridge and a Dimarzio next pickup and I think something is off with the push pull.

Shouldn’t the coil tap with the 3 way in the middle be hum free? I’m still hearing 60 cycle hum.

Any help would be appreciated.
 
It could be a few things. Could be something isn't grounded correctly.

Another possibility could be the direction and polarity is different between the different manufacturers. If that is the case, you would need to change the split to the opposite coil on one of the pickups.
 
You know, I'm pretty sure that McCartys didn't come with coil taps in 2000, I had two at the time. They certainly didn't come with Duncan and Dimarzio pickups.

So it's a modded guitar, and who the heck knows if it was correctly modded and wired? Lots of people do a pretty lousy job.
 
You know, I'm pretty sure that McCartys didn't come with coil taps in 2000, I had two at the time. They certainly didn't come with Duncan and Dimarzio pickups.

So it's a modded guitar, and who the heck knows if it was correctly modded and wired? Lots of people do a pretty lousy job.
This is the answer. Is there any volume drop in the middle position? If so they are out of phase. It’s likely a grounding issue if there is no volume drop.
 
Both Loocnmad and Garrett are at least partially correct and maybe 100% correct.

Test the screw polepieces of each pickup with the same pole or edge of a magnet. If it either repels from both pickups or attracts to both pickups then they are magnetically in phase. When the two pickups are in humbucking mode (not split) and are combined the sound should be strong.

If the magnet attracts to one and is repelled by the other they are magnetically out of phase. When the two pickups are in humbucking mode (not split) and combined the sound should be weak, thin and nasal.

When the two humbuckers are combined is the tone strong or thin? You want it to be strong.

Now take the magnet and check the polepieces of the two coils that are left on when the humbuckers are split.

The magnet should attract to one and be repelled by the other for it to be humcancelling when they are combined...just as one coil in a humbucker has a north polarity and the other coil south.

BUT they also need to REVERSE WOUND relative to each other to be humcancelling! The copper wire wound around the coil has a beginning and end. To be reverse wound, what is the beginning of one coil would be seen as the end of the other.

Hard to explain. But the two coils need to be RW/RP to be humcancelling when combined.

All that may not have been taken into consideration when the guitar was rewired.

I don't know if you can easily have it all: Two humbucking pickups that are in phase when combined and two singles that are humcancelling when combined. It would take some clever and somewhat complex switching and wiring.
 
Last edited:
Hi,

I just bought a used 2000 Mcarty with a Duncan bridge and a Dimarzio next pickup and I think something is off with the push pull.

Shouldn’t the coil tap with the 3 way in the middle be hum free? I’m still hearing 60 cycle hum.

Any help would be appreciated.
The middle position will only be completely hum cancelling if both humbuckers are tapped, each pickup’s tapped coils have a similar number of winds, and are wired in reverse polarity as has been said.

If only one is tapped, but of reverse polarity, the tone will be partially hum cancelling.
 
The middle position will only be completely hum cancelling if both humbuckers are tapped, each pickup’s tapped coils have a similar number of winds, and are wired in reverse polarity as has been said.

If only one is tapped, but of reverse polarity, the tone will be partially hum cancelling.
Wouldn't one of the two coils have to be reverse wound and reverse polarity relative to the other for them to be humcancelling when combined?
 
Wouldn't one of the two coils have to be reverse wound and reverse polarity relative to the other for them to be humcancelling when combined?
That's essentially the same thing. This is why the 5-way switching on 2 HB guitars generally offers both outer and both inner coils for the 2 and 4 positions to keep the hum cancelling in effect. They need to run against each other to cancel.
 
That's essentially the same thing. This is why the 5-way switching on 2 HB guitars generally offers both outer and both inner coils for the 2 and 4 positions to keep the hum cancelling in effect. They need to run against each other to cancel.
But they wouldn't be humcancelling unless one was reverse wound and reverse magnetic polarity. Right?

So is one reverse wound and reverse magnetic polarity?

If you had two identical humbuckers, combining a stud coil from one pickup with a screw coil from the other pickup would be humcancelling because one would be RW/RP compared to the other.

One coil in a humbucker is always RW/RP. That's what makes it buck the hum.
 
Last edited:
Right. Hence the two solutions I provided.


Adjust wiring to split one pickup to the other coil:

For coil split wiring, you can make the connection from the push/pull to ground or to hot. This cancels one coil or the other. Make this swap on one of the pickups and you'll have hum cancelling in the middle position. It makes an impact on tone as well, since a different coil is active in split mode, so you can have some fun experimenting to see what sounds best to you.

The other option here is a benefit of 4-conductor wiring. You can connect the pickup leads differently to reorder the coils. Seymour Duncan has their alternate wiring available on their site, or you can work it out with a multimeter. Why do this? You can leave the push/pull connection to ground, but shift which coil is active when split, which sometimes makes for cleaner wiring.

Bottom line here is if both pickups are same polarity (the typical way humbuckers are) you can have one pickup split to screw and one split to slug (Ibanez and Suhr both do this). Bam, hum cancelling!



Magnet flip:

This is how to get hum cancelling when you split both pickups to screw or both pickups to slug.

What PRS did with the Custom and all the incarnations of 5-way switching was to make one pickup reverse polarity. So one screw coil is north and the other screw coil is south. They're kept in phase by wiring one pickup in reverse of the other. This way, when you split to both screw or to both slug coils, you get hum cancelling.

You can do this with basically any humbucker set with some careful pickup surgery. Flip the magnet of one pickup and then wire it "backwards". Then refer to the first section above if you need to change which coil is active in split mode.
 
The reason I ask is that my '97 CE22 has Dragon pickups and the 5 position rotary switch.

Bridge humbucker
Screw bridge and screw neck - hums slightly
Slug bridge and slug neck - hums slightly
Slug bridge and slug neck
Neck humbucker

So three out of the five are humbucking and two seem to be not.

Or so it seems.
 
The reason I ask is that my '97 CE22 has Dragon pickups and the 5 position rotary switch.

Bridge humbucker
Screw bridge and screw neck - hums slightly
Slug bridge and slug neck - hums slightly
Slug bridge and slug neck
Neck humbucker

So three out of the five are humbucking and two seem to be not.

Or so it seems.

ViperDoc nailed it a few posts above. Unless the two coils are very similar, one of them will transmit more noise than the other one can cancel, so you'll still have some hum.

The Dragon Treble has a boatload of winds with very thin wire, while the Dragon Bass has a thicker wire with a more typical number of winds like a traditional humbucker. Because of that mismatch, the cancellation won't be perfect.
 
Back
Top