Tough wiring proposition - 4 way switch on CP Jag

[mr_sooty]

Ok so I need to wire a Fender Classic Player Jaguar HH Special with a 4 way switch to allow neck, neck and bridge in series, neck and bridge in parallel, and bridge. I've been using this diagram for the switch:



Here's the wiring diagram for the guitar:

support.fender.com/service_diagrams/jaguar/014-1710A_SISD.pdf

So to get the bridge ground wire for the switch I detatched it from the push pull pot that splits the bridge humbucker where that humbucker seems to be grounded. I ran a wire from the end of that wire to the 4way switch, and otherwise wired it as per the diagram. Everything seems to have worked, except for one problem. The neck pickup on its own sounds 'twangy', almost like a tele middle position. But when I tap with a screw driver it confirms that only the neck pickup is activated in this position. The neck roller control still seems to change the sound of the neck pickup to a more single coil type sound, but with the two coils on it doesn't sound 'fat' liked a neck humbucker should. Is it possible that something I've done has caused the coils in the neck humbucker to be in parralel instead of series? Or am I just hearing things?

Note, I'm replacing the three on off pickup switches with the four way. Also, the 'bare' wires on the fender wiring diagram don't exist.

Help!

[newey]

I detatched it from the push pull pot that splits the bridge humbucker where that humbucker seems to be grounded.

What "push pull pot"? Both HBs on the std diagram are wired to blend pots that blend it from a full HB to a SC sound, a variable coil-cut thing.

And, which wire are you treating as being the ground?

(Note that, for Fender HB wire colors, black and white ordinarily make the series junction between the coils. On the diagram you show, the neck HB is however wired "inside out", so as to cut to the opposite coil from the bridge HB)

[mr_sooty]

Sorry, I meant the roller pot. I figured the ground wires from the pickups were the ones going tongue grounded lug on the roller pot. So I've treated as hot the ones going to the kill switch. Therefore in the case of the neck pickup I've run the black as hot and the white as ground, even though that would seem unusual. Is this where I've gone wrong? But this is how it seems to be wired. Otherwise why is the white going to the grounded lug?

[mr_sooty]

The humbuckers go to the roller pots and then to the kill switch before going to the pickup switch. I've left the neck bucker as it was, and just treated the wire from the kill switch to the neck on off switch as hot. The bridge pickup I needed to run the ground to the switch, so I disconnected it from the roller (the green wire) and ran that to the switch.

[mr_sooty]

Do you think wiring the neck humbucker the stock way...ie, black and white to the roller pot, gree to ground, red to hot, would fix the issue? If so, why was it not an issue in the stock wiring?

[newey]

What you've done seems correct, at least as far as the neck HB goes. If you disconnected the bridge ground from the roller pot, then that should no longer work correctly. But you say the problem is at the neck. I'm stumped.

I've left the neck bucker as it was, and just treated the wire from the kill switch to the neck on off switch as hot.

That would, I assume, be the green wire to the on/off switch.

It sounds like you may have inadvertently messed something up at the neck HB without meaning to do so. Double check that you haven't loosened any of the connections to the neck blend pot in the process of dismembering this.

[ashcatlt]

Grab your meter and measure the thing! It's the easiest way to tell.

Once you sort that out, you might think about jumpering the 4-way from the "to volume control/bridge hot" connection to the unused lug on the other side. This shorts the bridge pickup when it's off, rather than leaving it hanging from hot.

[mr_sooty]

Jun 2, 2014 5:34:58 GMT -5 newey said:

What you've done seems correct, at least as far as the neck HB goes. If you disconnected the bridge ground from the roller pot, then that should no longer work correctly.

I did, but then ran that wire to the point on the switch where the bridge ground is supposed to go. The roller still works because the lug is still grounded, so it's still grounding the coil for splitting the humbucker, and the ground from the humbucker goes to where it should on the switch. It's just the neck that doesn't sound right. Argh, will have to do some sleuthing.

[mr_sooty]

Right, so the problem seems to be that the bridge pickup is still active when the neck pickup is on. I tried the jumper thing and it doesn't make any difference. I'm stumped. Does that unused terminal need to be connected to anything? I tried running it to ground and that just shorted out everything.

[ashcatlt]

The roller pot for the bridge pickup can't be connected to ground. It should be connected to the bottom of the bridge pickup.

[mr_sooty]

As in connected to the base plate of the actual pickup itself? Or just any ground point? So run a wire from the grounded lug on the roller pot to the underside of the bridge pickup?

[ashcatlt]

No, man! The bottom wire of the bridge pickup, which I think is the green one(?). The wire that you removed from the roller pot should go back there where it was, and all connections to ground should be broken. If the lug itself is bent over to touch the metal, it needs to be unsoldered and bent away. The bare wire should actually go to ground, but none of the four signal carrying wires should get there without going through the 4-way first.

Do you own a meter?

[mr_sooty]

Jun 3, 2014 7:49:11 GMT -5 ashcatlt said:

Do you own a meter?

Yeah, but don't really know what to do with it. I mean I can measure resistance and voltage but it doesn't always mean a lot to me, I'm pretty much a 'paint by numbers' guy when it comes to wiring. Like I'm looking at the switch diagram I posted and I have no idea why it even works. I understand a few basics, I pretty much get how a normal guitar circuit works, but this switch diagram doesn't make any sense to me.

So maybe if I run that bridge ground to the grounded lug on the roller pot and then run my 'bridge negative' from that same lug, but un-bend it from the pot?

[mr_sooty]

SUCCESS! That worked, thanks Ash! Legend.

[ashcatlt]

Jun 3, 2014 19:45:03 GMT -5 mr_sooty said:

SUCCESS! That worked, thanks Ash! Legend.

Yay! Sorry I didn't catch that earlier. You basically had some part of the bridge leaking through the pot to be in parallel with whatever else the switches were doing.

Reading those wiring diagrams can be pretty weird some times. If it was an actual schematic rather than a wiring diagram, it would be quite a bit easier. Like so:



That's exactly the same as the 4-way diagram you have, with addition of the jumper that I suggested, except that it also has the pickups and pots for a standard strat in there...

The trick is to imagine the output jack tip and sleeve as though they are connected together (they are, at the "amp end" of the cable, usually via a fairly large resistance) and then follow the connections through all the components in the schematic around til it makes a circuit. Actually, I guess you don't really need that. Just try to follow it from sleeve to tip (or tip to sleeve) and watch what components (pickups and pots) it goes through. Sometimes they branch off and make several parallel loops along the way. A little patience, and a little imagination to "see" how the switches make their connections, and you can work it out. You don't need to understand all the math and theory. It's just drawing circles.

Once you've got it wired up, the DC resistance between the tip and sleep of the jack can give all kinds of great information about what is connected and how at any given time. If you're going to do this a lot, you should try to cultivate a couple of habits:

1) Try to measure every component out of circuit if at all possible. In this case I probably would not have disconnected everything just to get the info, but some idea at least of what the pickups are supposed to be is very helpful.

B) Measure again after soldering but before actually buttoning everything back up. Ideally, you would get readings in every possible combination of switch positions, but in this case, I think you could probably just verify that each switch works independently.

III) Measure again after you put it back together and screw everything down tight. If anything changes, you know that something happened in installation, and usually it give you some idea whether you've caused something to touch something it's not supposed to or broken a connection somehow.

So, now that you've got the numbers, how do you know what they mean? How do you use them for troubleshooting? Well, at very least you post them here and ask one of us to help sort it out!

I couldn't find the "Brain Scan Through a Nostril" threads that went in depth on the theory, but for the most part you're just looking to see that the numbers for single pickup settings are somewhere close to what you know the pickups should be, and that the series and parallel totals are somewhere close to what you'd expect by applying the relevant formula per Series and Parallel Components. In actual practice, the totals will never be exact because any pots involved will tend to skew things a little bit. Usually, though, real wiring problems will lead to some large and obvious deviation from the expected values. In your case, we would probably pretty quickly have seen that the Neck only position was giving some very low numbers, and pointed us a little closer anyway.

[newey]

Ash-

I couldn't find the "Brain Scan Through a Nostril" threads that went in depth on the theory,

You couldn't, because ChrisK renamed those threads to the more formal and descriptive:

Discerning Strat-type Resistances

And the companion thread:

Discerning LP-type Resistances

[mr_sooty]

Thanks Ash, that's really helpful!