Return of: Guitar Wiring Issues

HRmusic90

21st Century Digital Boy
A few years ago I decided to use my cheapest guitar for experiments. I had always wanted to change pickups, tuning heads, etc. I also went a step further and put in all new pots, knobs and toggle switch. I did something wrong. I was getting some really awful noise out of it. I didn't know how to fix it, gave up and put it aside for almost a year. I then took it to one of my coworkers who's good with electronics. His best guess was that I burned out one of my pots. I was bummed that I had done that but glad I had something to go on. I bought four new pots and even a new toggle switch. I put everything together again (with all new wiring as well). I'm still getting an awful amount of noise. The noise goes away whenever I touch anything that's grounded, and it gets amplified when I grab any of the signal wires [the signal wires for the pickups (orange) or the output wire from toggle switch to input jack (blue/cyan)]. Here's what I've got:

GuitarWiring.jpg

I'm left-handed. Also, one of my mods was to remove the old 1/4-inch pots and replace with 3/8. That's why it's a bit cramped in there. It's driving me nuts! I miss playing this thing!
 
You have a multimeter? I'd start with simply confirming you've got the tailpiece grounded and all pot cases grounded to that and that's what's connected to the shield connector of the 1/4" output jack.

Set all pots on "10" and then check that resistance needs is ZERO for all things that should be connected to ground; and everything else you touch somewhere between 5-15k depending on pickups. This is easier if your multimeter has one lead with an alligator clip, but just keep one on the ground at output and start poking around. Look for something that's not reading zero that should be.

That's some pretty gnarly looking wiring there. I'd probably rip it out and start over, but maybe it's salvageable if you can tell us what's connected and what's not.
 
For starters, yeah the wiring is a mess. :)
But also, I don't see any of the lugs on the volume pots grounded.
Looks like a les paul style cavity, but volumes are on top and tones are on bottom. Traditionally both volume pots are closest to the neck and tones closest to the back.
Google a les paul electronics cavity pic and copy that.
Your soldering itself doesn't look half bad, no big globs or anything. But the layout is sloppy. Can't tell what's going where.
Also, braided wiring will go a lot towards making it more quiet.
I'd disconnect everything and start from scratch.
:D
 
Ok so being left handed would at least explain why your volume grounds are wired up in reverse.
Ok, back to noise. We have NO idea what exactly you consider noise. The perceived noise may just be normal.....or not. I'm not there to hear it and see whats going on.

First, on ANY guitar with passive pickups there is going to be a string ground. When you touch any metal part of the guitar including the strings, it will reduce noise. And of course if you touch any hotwire, it will make a noise. (But you generally don't go touching the hot when you're playing. Lol :D)
Thats normal.
However..... All your wires are single conductor without shielding. (adds noise)
Assuming everything is wired up correctly shielding on the wires and shielding the cavity itself will reduce noise.
How about your jack. That wired correctly?

Edit : I still say start over. Used braided wire. Also your switch has no ground. Needs to be grounded too.
 
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...Also your switch has no ground. Needs to be grounded too.

It doesn't? That's what the green wire coming off the top of the toggle switch and going to the neck-volume pot is supposed to be. Did I get that wrong?
 
I'm assuming the wire from the back of the switch to the pot case (purple in my attached markup) is the switch ground.

Still, any attempt to check this without confirming continuity and appropriate resistance (impedance proxy) is a guessing game. NOBODY should be doing wiring on an electric guitar without a multimeter. You can get one that will confirm continuity and resistance close enough for guitar work for under $10. The one I have (after my dear, 50 year old RCA bit the dust) was like $4 at Harbor Freight.

wiringhd.jpg
 
Ok, so I got a digital multimeter and checked the pots. It does read zero for everything that needs to be grounded. For my volume pots, I get about 3.4 k-Ohm open (i.e. pot at "10") and about 1.7 k-Ohm "closed" (i.e. pot at "0").

As for added noise, I plugged my guitar directly into my audio interface: my RME Fireface UCX. With no cable plugged into Mic/Line 2, it reads about -100 dB (with no added gain). With an instrument cable plugged in, it reads the same. With a known good guitar (my BC Rich Mockingbird), it reads almost the same -98/-97. With my WIP guitar, it reads about -85, so with my wiring the way it is, I'm getting about a 15 dB increase in noise.
 
Those DC resistance measures seem low to not right. Not sure what pickups you have but a single pickup shouldn't measure that low.

Here's a video that's Ok to show a LP where the individual pickups are measured. (You only have to watch from where it starts to the "Loose" title start.) You'll notice in the video that when both pickups are selected the resistance is about 1/2 - technically (r1+r2)/2 - so if you have the switch in the middle maybe that 3.4kΩ value makes a little sense.

YouTube

P.S. If those numbers persist on single pickup switch settings, you need to pull all that wiring and measure the pickups to see what they read individually, then carefully wire just the volumes and switch and confirm that's working correctly, then add in the tone pots one at a time, rechecking the wiring. Individual pickups should go to zero when volume is dialed all the way back.

The obvious question not asked yet is what are the pot values you're using? 500kΩ is typical for humbuckers, with an audio taper (IMO).

P.P.S. I'll say again I think it should be redone and cleaned up. I was looking closely at it and it seems like you've got you're volume pots wired together in some way, though it's damn hard to see what's going on in that rats' nest. See the orange wire that looks like it's attached to both where I've put the yellow arrows.
GuitarWiring2.jpg
 
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...though it's damn hard to see what's going on in that rats' nest.

Yeah, another thing contributing to the mess is the lack of space. The original guitar had smaller, 1/4 inch pots. These are the larger 3/8 inch.

The pots I'm using are Dimarzio "custom taper" pots. They're supposed to be 500 k-Ohm ±10% but I had a couple that have been a little out of spec (~437 k-Ohm).

What tips do you have for neatening up the wiring? I always cut my pieces too long because of course, better than too short. But it does leave a lot of slack.
 
Yeah, another thing contributing to the mess is the lack of space. The original guitar had smaller, 1/4 inch pots. These are the larger 3/8 inch.

The pots I'm using are Dimarzio "custom taper" pots. They're supposed to be 500 k-Ohm ±10% but I had a couple that have been a little out of spec (~437 k-Ohm).

What tips do you have for neatening up the wiring? I always cut my pieces too long because of course, better than too short. But it does leave a lot of slack.
Well, the larger pots would make it easier for some folks, even though the space is tighter, but you're not connecting wires on the side of the pickups, so the tightness really just means making sure the lugs on the pots are oriented so they don't interfere with each other.

I'd just disconnect everything and pull it out. Get some solder-sucking tool, maybe canned air and/or copper braid and clean off the pots as best as possible, without frying them of course. Lay them out in the cavity, or if it's easier, get a thin piece of plywood/masonite and drill holes to match your guitar and orient and wire up the connecting wires and caps with the pots on that, then drop that into the cavity.

Make sure you are keeping the "hot" wires fully insulated as close to the lugs as possible. You can use much smaller wire for these distances. I like solid copper, which you can unsheath and run a solid wire around all the pots for grounding, instead of a bunch of separate wires.

Tin the lugs and just enough stripped wire ends, pre-bent to fit into the lugs cleanly and just touch them with the hot iron to quickly melt a tiny bit of solder making sure nothing moves and you get a good, solid (not "cold") joint. trim off excess wire ends.
 
What tips do you have for neatening up the wiring? .

Take the pots out of the guitar and mount them on a board with the holes drilled to the same spacing of the guitar.
Do all your pot to pot grounds and soldering lugs to the casing outside of the istrument.
Pull the switch out, and rewire it with a braided shield wire. Being a little longer is fine, you can trim excess later.
Mark all the wires coming off the switch. A bit of tape and a sharpie can help. N (neck) B (bridge) J (jack)
Install your switch and pull the wires out of the way. Now install your pots.
Start with connecting all your shield to the pots, then the hots. Trim to proper leangth at this stage.
Take your time and it should turn out neat.
 
So here is my wiring, mostly redone...
Wiring_no_pickups.jpg
The only wiring that's missing are the pickups themselves. But I thought, before I do that. Let me see if I get any noise with just the components so far... I do :(
 
Is there a wire missing?
I can account for Switch out 1+2 (red+white?), switch ground (green?), and switch out passing through the cavity (blue?).
That means bridge ground isn't coming in...or green is bridge ground and switch ground isn't coming in.

Looks much tidier now. :)
 
So far as I can tell there isn't. The bridge ground is the black wire at the top, grounded to the top-left pot. That's the only original wire left from the original hardware.
Given that fact, it might be tempting to focus on that as the culprit, but I very much doubt it. That same wire was once originally connected to the old pots and I did not have this issue.
 
Sounds like a grounding problem.

Rip it ALL out. Use NEW smaller components.

Ground all Grounds to GROUND not another pot case.

Better yet make a board to hold everything that will fit in easily so you can solder neat outside and then only add a couple of solder joints when you put it in.

---------- Update ----------

It doesn't? That's what the green wire coming off the top of the toggle switch and going to the neck-volume pot is supposed to be. Did I get that wrong?

You got something wrong. The grounds look iffy the way you did it.
 
So far as I can tell there isn't. The bridge ground is the black wire at the top, grounded to the top-left pot. That's the only original wire left from the original hardware.
Given that fact, it might be tempting to focus on that as the culprit, but I very much doubt it. That same wire was once originally connected to the old pots and I did not have this issue.

Ah, I didn't spot the black wire. Even now that you point it out I can't see where it's coming from. I guess it's own little hold obscured from view by the pot?
Either way, it's there. Looks good to me, so far. :)
 
If you have nothing connected to the switch it’s just an open circuit. Bound to hum I’d think.

Just check continuity between the tailpiece and the sleeve of a guitar cable plugged in to the guitar. And that should also be open with infinite resistance when checked against the cable tip. (Unless you have wired up the pickups.)
 
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