Middle pickup selection output drop on CIJ JM after tech installed new pickups

[killianr]

I just got my guitar back from a tech who installed two new Curtis Novak pickups for mw. A JMV in the neck and a P90 in the bridge. He was following the Seymour Duncan diagram but couldn't get the rhythm circuit to work properly. We decided to bypass it and just wire the lead circuit leaving out the rest. Thing is that when I select the middle position of the pickup selector, i get a significant drop in volume. I assume this is not normal. Problem is I can't take it back as the work was done in Berlin and I am now in Dublin. I want to learn guitar electronics but wasn't planning to take on this project on my new JM.

Any ideas or help would be appreciated.

This forum is awesome.

[Nord]

I'm not an expert, so others will have to chime in, but it sounds like the pups might be wired in parallel, not series. Wired in series they'd be out-of-phase and reduce hum. In parallel volume would drop and you'd notice a slight nasal tone...

[theworkoffire]

Hang on Nord - the pickups in a Jazzmaster shouldn't be wired in series. They should be parallel but in phase, and if you get a thinner sound in the middle position you might have them out of phase. It could also be a problem with how the 3-way switch is wired up.

Can you take the guard off and take pictures that will clearly show the wiring?

And there's really no reason why you should have to suffer incomplete wiring just because your tech couldn't work it out.

[Nord]

Thanks for clearing that up theworkoffire. Warned ya that I'm not an expert 
I would guess that the 3-way wiring might hold the answer here

[killianr]

Thanks for the suggestions. Looks like i'll have to take a crash course in guitar electronics. I won't be able to take pics until the morning. Meanwhile this is the diagram he was supposed to follow. My guitar doesn't have shielding tubs so the ground was wired differently.

[killianr]

and perhaps you could also tell me how to add images !

[theworkoffire]

and perhaps you could also tell me how to add images !

You need to post them up on a hosting site like photobucket then link to them between the img tags.

[jetset]

Standard pairs of pickups are wired so they will be both in-phase and hum canceling in the middle position.  Mismatched pairs (like you have) could be installed correctly but be wound differently so as to be out of phase (which would account for the volume drop).  I'd send a quick email to Curtis and let him know the exact pickups and he'd probably be able to suss it for you. It may be as simple as swapping the black and white (hot and ground) wires from one of the pickups at the selector switch.
-j

[jbuckner]

Your pickups were wired wrong and they are out of phase.

It's a easy fix. You can find the wiring schematic on SeymourDuncan.com.

[killianr]

could it be that he switched ground and hot on one of the pickups ? he wasn't sure which was which. to be fair, there was no indication when they were shipped which was which. i found out later but it wasn't in time as he had already replaced the pickguard. he seemed to think though that it was as it should be. have decided to wait  a few days before pulling it apart to take pictures. i want to play it. i assume that an incorrectly wired guitar isn't likely to cause any damage.....

what would be really useful to me as well is some documentation that shows what is actually going on in the guitar circuit. i have read everything i can find but its been pretty useless. theres lots of stuff that show this wire connecting to that lug etc but nothing i have seen that explains why. guitar signal flow seems to be very different to other stuff i have worked on.

thanks for the help so far. hopefully in a few days i'll get the courage to fix it myself. i really think there is no other way ultimately, i just didn't want to start at this time on a new guitar.

so many guitar techs seem to be really average at best. to be fair to this guy, his setups are good but he doesn't know electronics.

[theworkoffire]

Yes - to switch the phase all you do is swap the hot and ground wires over on the pickup, so more than likely that's the problem.

As for the wiring, these drawings might be helpful:

http://www.fender.com/support/diagrams/ ... 00APg4.pdf
http://www.fender.com/support/diagrams/ ... 00APg2.pdf



Think of the rhythm switch as two separate switches side by side.

One side (bottom 3 lugs on this Seymour Duncan drawing) takes the output from the neck pickup and sends it to either the 3-way solo switch (and the lead vol/tone) or direct to the rhythm vol/tone. At the same time the other side (top three lugs) connects the output jack to either the 3-way solo switch (via the lead vol/tone) or to the rhythm vol/tone.

If you follow the wire from the neck pickup on this drawing and when you get to the switch take it left you can trace the signal via the 3-way, through the lead vol pot, back up to the switch and then out to the jack. If you take it right at the switch you trace the signal through the rhythm vol/tone, back to the switch and then out to the jack.

Does that help?

[killianr]

thanks, thats a good explanation. the penny hasn't quite dropped but i'll keep looking at it until it sinks in !

is there any rescources that explains how these things work ?

ie which lug does what and why.

everything i've come across just tells you to wire this to that but doesn't explain why.

grounding seems to be at the heart of these diagrams but i never can tell what each ground is for.

there seems to be two types of ground - a 'component' type one to stop parts from making unwanted noise.

and an 'effect' type ground (say, with a capacitor) that bleeds part of the signal to ground (say in volume and tone pots) to facilitate signal processing for want of a better word.

am i on the right track ? i would love to get to know this stuff better.

[RumorsOFsurF]

I just had the same experience.  I'm pretty sure I just have the ground and hot wires reversed.  The pickup I bought from Curtis has green and yellow leads....I just ran the wires like in the diagram, and apparently it wasn't right. 

I'm going to pull the thing apart tomorrow and switch the wires.