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Wiring help needed


Xanthus
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So I needed to rewire my V for two reasons: I got a new bridge pickup, and there was some annoying humming that I'm thinking was ground loop-related. Buzzing until you touch the strings or metal parts, stuff like that.

So I'm just doing a refresher on what I need to do, when I decide to check the Stewmac site to double-check everything. And it turns out that the wiring diagram on their site is nothing like the one they sent me when I ordered the switch.

The changes are:

-tone cap is now between the middle tone lug and the ground volume lug, as opposed to the back of the tone pot.

-switch lug 4 is now the bare wire from the bridge pickup, not the green wire (Dimarzio color codes)

This is what really gets me. The instructions for lug 4 say "ground w/o shield" yet the picture says to solder the bare wire. Dimarzio's color code says the bare is the shield, not ground.

That's where I'm caught up. I'm pretty sure I'm going to disregard the tone cap change and do it the old-fashioned way. But the switch lug is really what gets me. Could this have been what caused my buzzing problem? I don't THINK so, but then again.....

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lug 4 should be the ground wire from the pickup (the green wire) not the sheild, the sheild should go directly to ground and not be connected up to the selector. You need to connect them up like this because of how the switch gets all the fancy differant coil combinations (in this case outer coils only I think but I'd have to trace it to be sure). The tone cap is electronicly in the same place they've just drawn the layout differantly

As for ground loop problems my advice would be to make sure that all your grounds connect to the output jack by one route and one route only. I also always use sheilded wire, makes it more difficult working out how to ground things to prevent loops but its less work than sheilding the whole cavity.

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Thanks, Rob. I never knew that about the tone cap, I thought it was a totally new setup entirely :D

I'm going to be doing star grounding on this one, to make absolutely sure I avoid loops. I like GregP's theory behind star grounding: It's not easier to install, but it let's you see what's going on much more clearly.

You're right about the coils, it is outer only. Thanks for the clarification!

Also, as a side note, I'm almost positive the metal(lic) casing that surrounds all of the wires doesn't need to be shielded... right?

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The metalic-y sheild inside the cable will be in contact with the bare and is grounded with that. That's basicly what the bare in these pickups is for.

I've done various differant star grounding styles before, everything from soldering all the grounds to a screw in the middle of the control cavity to quite complicated 'tree' styled star grounds (damn Les Pauls!). Defenatly the way to do it though!

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Wondering if I could bug y'all for one last question.

On my diagram, can I just bridge the ground from pot through killswtich to jack, like I did the hot wire? Or does the T-Junction need to be there for it to function properly?

so long as there's a wire going from the pot to the lug then from the same lug to the jack it'll be fine. Shouldn't make any differance what so ever.

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Yeah, so I changed the name of the topic. Why? Because I'm a mother-lovin' moderator. Trying to attract attention from someone other than Robert :D

Onto the issue at hand. I rewired the V yet again, and my diagram now looks like this. Note the star grounding. Well, I'm now getting WORSE hum than before. When I don't touch the strings, when I DO touch the strings, when I play a chord... I even dug out my Pod and used its noise gate with max settings. The major hum goes away, but this high pitched hissing, white noise still comes through. My dad went poking through the cavity with a jumper wire. He found out that when he touched the back of the tone pot to the ground lug on the killswitch, all of the hum went away! He then found out that it was because he was touching the metal part of the jumper wire. So, back to square one. We've come up with these possibilities.

-Maybe the new StewMac diagram is right (see the first post) and I need to switch the ground and bare wire from the bridge pickup.

-Maybe the lug on the P switch that SM says isn't used needs to be grounded? I did see a diagram, not from SM, that said it does

-Moving the tone cap to bridge the tone pot and ground lug of the volume pot (I doubt it, but thought I'd throw it in there)

-mixed up the ground and hot coming from the jack (99% unlikely. wouldn't the guitar start to like... smoke or some crap?)

-futzed up something with the star grounding? It's securely soldered and wrapped in electrical tape...

-Maybe I need that T-junction like in my original diagram for the circuit to work? Again, almost positive this isn't the case.

I'm honestly all out of ideas, and running desperately low on patience. It's been nigh a month since it was completed and I still can't play it and it STILL needs nut and fretwork too..........

::EDIT::

I'm sending StewMac an e-mail with a big "what the?" as we speak.

Edited by Xanthus
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Before reading this - you're sure you had no noise prior to installation? Just making sure the ground was good to start with - not trying to offend in any way!

-Moving the tone cap to bridge the tone pot and ground lug of the volume pot (I doubt it, but thought I'd throw it in there)

Not likely, unless its not soldered correctly, but there is some evidence that placing them between the pots, as opposed to just connecting on the tone will create more consistent tone at all levels of volume.

-Maybe the new StewMac diagram is right (see the first post) and I need to switch the ground and bare wire from the bridge pickup.

I'm liking the StewMac diagram as it seems "logical" that it would be accurate. Rob is correct too that the bare is connected to the sheilding on the pickup. Why? Coils. Gotta ground them separately to split them. Otherwise, makes a clean path for grounding all shields and gives you the opportunity to ground it in the cavity using sheilding or sheilding paint? Not sure, but I always ground them both. Have put quite a few DP-100s, DP-318s in this way, even using p/p pots for coil switching with no noise at all.

In the StewMac diagram, 4/5 appear to be for ground as 4 accepts bare from pickup and 5 is grounded to pot. For grins, ground them commonly. It won't allow the coil, but could rule out poor grounding at the switch.

-mixed up the ground and hot coming from the jack (99% unlikely. wouldn't the guitar start to like... smoke or some crap?)

Most likely no sound and possibly some slight tingling on the fingers :D Possible though that jack is bad, but you would have prob. noticed before upgrade.

-futzed up something with the star grounding? It's securely soldered and wrapped in electrical tape...

is it far enough away from the pickups? just a thought - I've always had better luck star grounding in the back cavity near trem springs

To test - eliminate the kill switch. Pretty easy to solder it back in, but process of elimination....

*** EDIT ***

One more thing, make sure there's absolutely no loose solder or wire pieces making any undesired connections anywhere - just making sure. :D

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Thanks for the quick reply, KP! I'm going to make this brief, because work calls at 5:00 tomorrow morning.........

you're sure you had no noise prior to installation?

No, I had noise the first time I wired it up. That's half the reason I took it apart again, the other half being I got a new pickup. I switched to star grounding after the first time, thinking it would solve any ground loop I might have run into.

there is some evidence that placing them between the pots, as opposed to just connecting on the tone will create more consistent tone at all levels of volume

That's pretty interesting, I never heard that before. My EMG pots came wired with the cap bridged, but I thought the back of the tone pot was the "traditional" place to put it. huh.

I'm liking the StewMac diagram as it seems "logical" that it would be accurate

See, I'm thinking that more and more. I just got finished with sending them an e-mail, hopefully I'll get a response before I get back from work, else I'll call them.

For grins, ground them commonly.

....huh? I'm totally not an electronics guy. How would I go about doing that?

I'm pretty positive that the killswitch is fine, because it's brand new, and the star grounding is about as far away as I can put it in the cavity.

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Instead of grounding lug 5 to the V pot, send it straight to the star ground. Lug 4 is grounding a coil from a pickup (based on diagram and DiM wiring) instead of grounding through the switch (which is what you're doing to enable a different sound) send it straight to the star as well. You won't get a coil split, but could help eliminate switch problems. 5:00? Ack - I'll be at it at 7:00

Also - if you had noise before putting in the new pickup/switch - make sure the connection at the bridge is good.

One last edit - to be clear in your diagrams, I'm assuming that the black line going to ground is bare and the black/white is the DiM instructed series connection.

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To confuse things futher I thought I'd do you a wiring diagram. Hopefully this will clear things up, I've used the back of the volume pot as the main grounding point then chained the ground along the other components (this cuts down the number of wires in your control cavity). My suggestion would be to take out all the wiring and start again completely from scratch. Follow one of the diagrams and mark each wire as you soldier it in place.

+++ BAD DIAGRAM DELETED NEW ONE ON ITS WAY+++

All the wires from the humbucker are the correct colour code, other wires have been done in differant colours just to make things clear. Wires crossing eachother don't join wires only join on lugs of components.

By the sounds of it you may have got your ground and signal mixed up on the output jack, you will get a lot of noise that way!

there is some evidence that placing them between the pots, as opposed to just connecting on the tone will create more consistent tone at all levels of volume

As I'm doing a degree in Electrical and Electronic Engineering I'd like to see that 'evidence' :D connecting to ground is connecting to ground.

Edited by Robert_the_damned
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As I'm doing a degree in Electrical and Electronic Engineering I'd like to see that 'evidence' connecting to ground is connecting to ground.

I'm sure you've heard most of this, it's just here to make sure I didn't miss something myself :D

If you connect a cap to a pot - as is done with connecting a cap from lug to ground - you are enabling the filter capabilities of the cap. Not knowing the exact cap being used - one may assume industry standard numbers of between .022 and .047. History also shows us that these caps are generally only effective when the tone control is activated (almost all the way).

The article I was referencing was a just that - an article in a magazine (I am still searching and will try to scan/transpose) where the question was posed regarding placement of caps on or between pots. The further question was, since a tone pot is used with a cap to create a "treble bleed" whereby certain frequencies are sent to ground to prevent transmission through the guitar jack, would it be logical that the cap would be placed between the pots to prevent or promote such a dramatic response in the tone pot behavior?

Basically - what impact would limiting the signal to the tone pot have on overall tone response? Almost any single-coil player can make this happen on by noticing a sharp drop in brightness when using the tone pot. In this case - would a resistor (added to the capacitor) be more appropriate?

Some experiments were done some results included as far as frequency transmission. You are correct, ground is ground, but what happens between device and ground is more what I was referencing. Not sure it's such a far fetched idea as I keep getting guitars brought in for pickup replacement that have the cap from lug on v to lug on t. This does not create a grounded circuit - until the same lug on v is jumped to the case of the pot. Theoretically, this could have a potentially different effect than connecting the pots via wire.

I apologize if this created/caused any concern.

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Why does that schematic look deceptively simple, Rob? :D Is it because my control cavity is the relative size of a postage stamp? hahahaha

If the general consensus is the mixing of hot and ground, I'll switch them before tearing apart my wiring. I had a few questions, though, seeing as questions are the order of the day 'round here.

-When grounding the bare and green wire, I wrapped them in electrical tape and grounded them as one wire. Yay or nay?

-There's no bridge ground...

-Why isn't the hot of the volume attached to the center lug?

-Is the hot wire T-junction at the tone pot crucial, or can I run it through the lug like the volume pot?

The diagram seems simple enough, if switching the hot and ground doesn't solve the problem. I don't want to burn out the little killswitch with too much heat/repeated soldering though. Such fragile little Radio Shack switches :D

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-When grounding the bare and green wire, I wrapped them in electrical tape and grounded them as one wire. Yay or nay?

soldier them then put tape on would be my advice, tape can and will work loose over time and then you'll loose the connection.

-There's no bridge ground...

I forgot that woops! (you can tell I've not done these for a while eh?)

-Why isn't the hot of the volume attached to the center lug?

because I wasn't paying attention obviously :D oh boy does this diagram suck :D (note to self must try harder B) )

-Is the hot wire T-junction at the tone pot crucial, or can I run it through the lug like the volume pot?

either way is fine, so long as everything is connected it doesn't really matter to much as to how its connected.

The diagram seems simple enough, if switching the hot and ground doesn't solve the problem. I don't want to burn out the little killswitch with too much heat/repeated soldering though. Such fragile little Radio Shack switches B)

so long as you don't start melting the casing (when stuff inside will probably start moving) it should be fine.

New (hopefully correct rather than a load of "£$*&^ diagram)

wiring1-1.png

Edited by Robert_the_damned
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sorry for double posting guys!

Some experiments were done some results included as far as frequency transmission. You are correct, ground is ground, but what happens between device and ground is more what I was referencing. Not sure it's such a far fetched idea as I keep getting guitars brought in for pickup replacement that have the cap from lug on v to lug on t. This does not create a grounded circuit - until the same lug on v is jumped to the case of the pot. Theoretically, this could have a potentially different effect than connecting the pots via wire.

I apologize if this created/caused any concern.

No concern at all, just that the cap in the Stew Mac diagram is connected from the lug on the tone pot to the lug on the volume pot which is then connected to the star ground, meaning that the 'volume' end of the cap is grounded. Hence why wiring it this way shouldn't make any differance.

:D I never use my tone pot in anycase so it matters little!

Edited by Robert_the_damned
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ah yes my V is just an 81 and a vol pot :D

If you happen to find that article I'd be interested in having a look at it, I've got an oscilascope and some caps and pots so it wouldn't take much for me to do the experiment for myself.

Shame you're not a bit closer - I have a bucket full of pickups we could measure frequencies against coil counts as well - would make an interesting read if nothing else. I will continue my search.

Wire from volume to tone should be on the opposite lug of the tone pot..?

I'm thinkin' that's the ground lug. Diagram take 2 makes sense.

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there is some evidence that placing them between the pots, as opposed to just connecting on the tone will create more consistent tone at all levels of volume

As I'm doing a degree in Electrical and Electronic Engineering I'd like to see that 'evidence' :D connecting to ground is connecting to ground.

I agree. The metal casing on all pots should be electrically connected to ground, therefore, they are also electrically connected to each other. It will make not one jot of difference to the tone whether you ground the cap on the volume or the tone pot.

Just some comments on other stuff in this thread. The value of the tone pot and the cap together form a low pass filter (as someone said, it 'bleeds' the high frequencies to ground). As you turn the tone pot, it's value changes, because you are using the wiper (centre) lug and one of the fixed end lugs, and this changes the frequency at which the filter starts to cut off the highs. One thing that will effect how quickly this is heard as you turn the pot, is where, in the audio frequency band that the guitar produces, that variable frequency actually falls (if it falls outside that band, e.g. higher, little difference will be heard as all the guitars sound is let through), and as said, this is determined by the resistance of the pot and value of the cap. (eqn's and diagrams here http://en.wikipedia.org/wiki/Low-pass_filter) Another thing that will effect it, is the "taper" of the pot. They most commonly come in linear and logarithmic (also known as audio taper). For the volume control, you need the audio taper because your ears perceive the change is sound level logarithmically

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Exactly - this is a well established principle. The metal casing is connected to the ground - so is everything else. The question is does it matter if the cap acts differently by controlling the bleed between the v/t pots than it does by simply bleeding off the tone pot via ground. That's all.

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Wire from volume to tone should be on the opposite lug of the tone pot..?

I'm thinkin' that's the ground lug. Diagram take 2 makes sense.

I'm not so sure about this one..... In all the diagrams I've seen (taking the orientation of the pots in Rob's diagram into account), the "left" lug of the volume is connected to the "right" lug of the tone.

Other than that difference (and star grounding) my current wiring setup is the same. I just checked to see if the bridge ground was good. My dad expressed doubts, because the bushings were powder coated. Also, no hissing or tingling fingers, so the jack is wired correctly. Everything is exactly like the diagram.

I'll try switching around the tone lug, but I doubt that will do anything. Hoping I have time tomorrow, I'll un-ground everything, get rid of the star setup, and re-ground everything to the pots.

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Exactly - this is a well established principle. The metal casing is connected to the ground - so is everything else. The question is does it matter if the cap acts differently by controlling the bleed between the v/t pots than it does by simply bleeding off the tone pot via ground. That's all.

If you mean that you connect the signal from the volume pot to the tone pot via a cap, that can't work, because it will form a high pass filter, not a low pass (tone control).

but it's hard to know without a diagram

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I'm not so sure about this one..... In all the diagrams I've seen (taking the orientation of the pots in Rob's diagram into account), the "left" lug of the volume is connected to the "right" lug of the tone.

Other than that difference (and star grounding) my current wiring setup is the same. I just checked to see if the bridge ground was good. My dad expressed doubts, because the bushings were powder coated. Also, no hissing or tingling fingers, so the jack is wired correctly. Everything is exactly like the diagram.

I'll try switching around the tone lug, but I doubt that will do anything. Hoping I have time tomorrow, I'll un-ground everything, get rid of the star setup, and re-ground everything to the pots.

Using the opposite lug on the tone control will make it work the other way, i.e. backwards.

I scraped the powder coating off one groove of the bushing to make sure it got good contact, when I grounded my painted tailpiece.

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