Wiring question...tone pot acts like volume

rpbarry58

New member
I recently acquired a Gibson Sonex 180 Custom both out of nostalgia purposes (I had one 25 years ago) as well as the fact that I wanted to harvest the Dirty Fingers out of it for my LPC. After I pulled the Dirty Fingers pickups, I decided to transplant the neck SH-1 and bridge SH-4 out of my LPC into the Sonex just to keep it alive and kicking. Everything worked, but the pots were scratchy and cheap and the pickup selector switch was on it's way out plus the coil tap switch was bent 45 degrees off axis. So I went ahead and reamed out the small holes and installed two CTS 500K linear taper volume pots and 2 CTS 525K audio taper tone pots from The Art Of Tone. This model Sonex had the coil tap switch so I connected the white and red wires from the SH-4 to one of the new DPDT switch's upper lugs and sent the lug below it to ground via the ground terminal of the jack (this was how it was wired with the Dirty Fingers). Obviously the SH-1 isn't tappable. So when I fired it up, the tone control for the neck SH-1 is basically acting as volume pot...but it is not grounded out anywhere! I changed the pot from the 525K to a standard CTS 500K I had lying around, used the stock green chicklet tone cap, a Russian PETP cap, an orange drop and even a CD Black Cat I had laying around. Tried several different wiring diagrams for Gibsons; '50s, modern, all with the same result. The only thing I can think of is somehow it's because the SH-4 is being half grounded when tapped and the SH-1 is not? Doesn't matter whether the tap is engaged or not though...tone pot does not roll off any treble, and as a matter of fact the treble that is there is more than I've ever heard out of a neck pickup. Volume works fine in the neck pickup circuit and the bridge circuit works perfectly.

Can anybody think of what might be the case here? I checked immediately to see if the tone pot was grounded out somehow and it's not and I even changed it out in case it was a bum pot. What am I missing.
 
Re: Wiring question...tone pot acts like volume

Tore the whole setup down and started over today from scratch. Double and triple checked grounds, made sure the ground lead from the tailpiece was firmly soldered on the volume pot for the neck pickup. Re-did all the wiring.

Same results. Bridge SH-4 humbucker circuit works perfectly. Coil tap switch does it's job, pickup select toggle switches fine. But the neck SH-1 is super bright still and the neck tone pot is still working more like a volume.

So if I messed up the first time I somehow replicated it exactly the second time...I'm thinking there is something else going on here.
 
Re: Wiring question...tone pot acts like volume

Sorry, forgot...I did take pics after a re-doing it today. Ground wire to the tailpiece isn't attached yet (has to be done with the pickguard over the cavity).Photo Mar 04, 1 38 40 PM.jpg
 
Re: Wiring question...tone pot acts like volume

I don't see what wires are connecting the pot grounds to the jack ground. Are you trying to depend on the pickguard shield to ground the pots?
 
Re: Wiring question...tone pot acts like volume

Yeah I have a handful of the green chicklet caps, tried all of those, some orange drops, some Russian PETP caps left over from a JCM800 build, all in 0.022uF plus a Black Cat in 0.015uF (which I prefer over 0.022uF) and none of them made any difference.

Definitely not relying on the shielding to ground the pots...the yellow, green and grey leads all have a white wire and bare wire inside. I ran the bare wire from the jack ground to the ground lug at the toggle switch, spliced it with the bare wire inside the yellow and green leads and soldered it to the ground lug. Hot white wire from the jack went to the hot lug on the toggle. The yellow and green leads coming from the switch have the bare wire soldered to the backs of the volume pots (see photo). I soldered the green and bare wire from the SH-4 to the same location on the bridge volume pot.

Photo Mar 04, 1 38 40 PM (1).jpg
 
Re: Wiring question...tone pot acts like volume

Have you checked the earthing for continuity ? Does it test from the jack to all other ground points ?
It looks like it should work
 
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Re: Wiring question...tone pot acts like volume

Have you checked the neck pickup for an actual resistance measurement from each coil?

I had this happen on a 1 hum. 1 vol. 1 tone guitar where everything was working, but sounded "off" and the tone knob acted like a volume control as well.
Well, the pickup was "working" in the sense that I got sound out of it, but when measured there was no resistance in either coil meaning an open, or broken coil wire.
Put in a different pickup, and everything worked fine.
 
Re: Wiring question...tone pot acts like volume

A tone pot acting like a volume pot is usually caused by accidentally getting the wrong cap value. For example, a .22uf cap, instead of a .022uf cap, will cause that exact symptom. Same for .047, .033 etc. Leaving out that zero will do that.
 
Re: Wiring question...tone pot acts like volume

WiringLP.jpg

Do I see correctly that all these pots are grounded there? If so, that's obviously causing the problem.

EDIT: Sorry, it's not that. Didn't look close enough...
 
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Re: Wiring question...tone pot acts like volume

So I decided to keep the wiring as is but pulled the SH-1 out, and popped the neck Dirty Fingers back into the Sonex. Works perfectly, taps and all. I put the SH-1 back into the neck of my Les Paul custom and the other Dirty Fingers in the bridge wired them up...I had installed two CTS push/pull tone pots because I was planning on using the tap with both Dirty Fingers so I left the neck one in and just wired to the lugs like normal, then wired up the bridge DF with the tap. Bridge pickup circuit works fine, tap works (that was kind of a pain to wire). Neck tone pot AGAIN acts like a volume control. So this same pickup is doing the same thing in a different guitar and wiring setup. Still very bright and harsh for a SH-1 in the neck position. Maybe the pickup is just cursed.
 
Re: Wiring question...tone pot acts like volume

It's the curse of the open coil :scared: lol
Really, if you measure the pickup I bet you'll find one (most likely) or both of the coils open.
 
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