les paul harness, but tone knobs adjustment doesn't work

[zirltzn]

i installed a jimmy page harness, jonesyblues.com-JIMMY_PAGE_WIRING , in my les paul. works good and sounds good except for the normal tone controls from 1..10 don't alter the tone at all.

i emailed jonesy and he said the paint i used to paint the cavity probably was affecting the ground. i put plastic washers on all the pots on the inside so that none of them touch the paint. note: i have some strats that have the same cavity paint and p/p tone pots and those tone knobs can adjust the tone all day long.

if i put a meter on the tone pots and turn the knobs they do show they work, at least in that type of test.

but plug it into an amp and i can not adjust the tone via those two tone knobs but all the options from the harness works.

thought i'd post here and get some ideas of how to fix this

[newey]

Do the tone knobs do anything at all as they are turned down, like affect the output? Or is it as if you weren't turning a pot at all?

[zirltzn]

Apr 28, 2014 22:33:03 GMT -5 newey said:

Do the tone knobs do anything at all as they are turned down, like affect the output? Or is it as if you weren't turning a pot at all?

nope, no diff when turned down at all. its as if i'm not turning the pot at all

[newey]

Maybe a couple of photos would disclose the problem, otherwise I'm at a loss. I assume there's nothing obviously wrong with it to a visual inspection, though.

If there was a dead short bypassing the cap, it wouldn't adjust the tone, but it would still act like a wonky volume pot. If the tone cap were disconnected at one end, it could give what you describe, but it's hard to imagine two independent identical faults occurring simultaneously.

Or, another thought, perhaps whoever made the thing grabbed two of the wrong value caps. Can you read the value?

[ashcatlt]

Apr 30, 2014 5:32:29 GMT -5 newey said:

If there was a dead short bypassing the cap, it wouldn't adjust the tone, but it would still act like a wonky volume pot.

Sure it will. It'll act almost exactly like a Tone control for the first half or so of the rotation, then it'll start to head toward silence.

If the tone cap were disconnected at one end, it could give what you describe, but it's hard to imagine two independent identical faults occurring simultaneously.

Unless the whole thing depends on both tone caps finding ground via the pot cases. My real LP has a metal plate that all of the pots contact and provides what is essentially a star ground. This OP has deliberately broken that connection. You can either remove those plastic washers, or run wires to a real ground point.

[zirltzn]

Apr 30, 2014 5:32:29 GMT -5 newey said:

Maybe a couple of photos would disclose the problem, otherwise I'm at a loss. I assume there's nothing obviously wrong with it to a visual inspection, though.

If there was a dead short bypassing the cap, it wouldn't adjust the tone, but it would still act like a wonky volume pot. If the tone cap were disconnected at one end, it could give what you describe, but it's hard to imagine two independent identical faults occurring simultaneously.

Or, another thought, perhaps whoever made the thing grabbed two of the wrong value caps. Can you read the value?

i'll take a few images and get them loaded up

[b4nj0]

Shorted capacitor has to mean no treble roll off.
The point regarding the grounding is on the mark though. Is the dreaded screening paint grounded because as has been written, the pots may share the same ground return. As ashcatlt said, take out the insulating washers or at least run separate ground wires to a common ground point. Has the continuity between the paint and the output jack socket ground lug been established?

e&oe

[zirltzn]

Apr 30, 2014 5:32:29 GMT -5 newey said:

Maybe a couple of photos would disclose the problem, otherwise I'm at a loss. I assume there's nothing obviously wrong with it to a visual inspection, though.

If there was a dead short bypassing the cap, it wouldn't adjust the tone, but it would still act like a wonky volume pot. If the tone cap were disconnected at one end, it could give what you describe, but it's hard to imagine two independent identical faults occurring simultaneously.

Or, another thought, perhaps whoever made the thing grabbed two of the wrong value caps. Can you read the value?

the caps are VitQ pio 22 for bridge and 15 for neck.

ok, here's a few images:

[newey]

Has the continuity between the paint and the output jack socket ground lug been established?

Or, even more basically, between the tone pot's shell and the output jack(-).

Ash's point about the washers is dead on, I had misunderstood what zirltzn meant when he described the current set-up. So Z does need to check for proper grounding, and probably in a number of places along the line, from pot to paint to output.

[zirltzn]

May 1, 2014 13:36:48 GMT -5 b4nj0 said:

Shorted capacitor has to mean no treble roll off.
The point regarding the grounding is on the mark though. Is the dreaded screening paint grounded because as has been written, the pots may share the same ground return. As ashcatlt said, take out the insulating washers or at least run separate ground wires to a common ground point. Has the continuity between the paint and the output jack socket ground lug been established?

e&oe

>Has the continuity between the paint and the output jack socket ground lug been established?

i don't think the output jack socket ground lug is has continuity with the paint, and it shouldn't right?

i did put in plastic washers on the pots hoping that would remove them from touching the paint, but might have goofed up elsewhere

i put the paint in to stop the crackling when touching the strings. that issue appears on the net with quite a few lp owners. now, i eliminate one problem and have another. ;-)

[zirltzn]

May 1, 2014 18:18:31 GMT -5 newey said:

Has the continuity between the paint and the output jack socket ground lug been established?

Or, even more basically, between the tone pot's shell and the output jack(-).

Ash's point about the washers is dead on, I had misunderstood what zirltzn meant when he described the current set-up. So Z does need to check for proper grounding, and probably in a number of places along the line, from pot to paint to output.

well, i replaced the metal washers and put plasic ones in. put blue tape in switch cavity so the switch wasn't touching paint.

as for the output jack .. that needs to be not touching any paint, right? or?

[b4nj0]

The screening paint is trying to assimilate a Faraday cage. I believe that it has to be "grounded" to function as a screen. If you are using the screening paint for the pot grounds, then it must be grounded too. The washers have to go (ideally) or be replaced by grounded wires.

e&oe

[newey]

Yes, the shielding paint needs to be grounded. And, while signal can certainly be carried that way as well, it's not a good idea to do so.

My suggestion would be to run separate ground wires from the back of the pot shells to a grounding point, and then to separately connect the paint to ground. Leave the washers as is.

The pot shells can simply be daisy-chained from one to another.

[ashcatlt]

May 1, 2014 13:36:48 GMT -5 b4nj0 said:

Shorted capacitor has to mean no treble roll off.

Are we talking about normal passive pickups with an inductive coil of wire wrapped around a magnet? Is the variable resistance of the T pot parallel to the pickup and output jack? Then reducing that variable resistance absolutely will lower the cutoff frequency of the RL low-pass. Ever heard of tone suck? Ever plugged straight into a line input? The tone cap doesn't really have any effect on the circuit till the variable resistance gets pretty small.

[b4nj0]

Yes I think we are. Would it be one where there is an induced voltage in the coil or one that is current fed?

e&oe

[ashcatlt]

It would be modeled as an ideal voltage source in series with a large inductor in series with a largish
resistor with a smallish capacitor parallel to them.

[zirltzn]

May 2, 2014 5:44:41 GMT -5 newey said:

Yes, the shielding paint needs to be grounded. And, while signal can certainly be carried that way as well, it's not a good idea to do so.

My suggestion would be to run separate ground wires from the back of the pot shells to a grounding point, and then to separately connect the paint to ground. Leave the washers as is.

The pot shells can simply be daisy-chained from one to another.

ok, i'm getting a better handle on this, thanks

the pot shells are daisy-chained from one to another. probably very hard to see in the images i took.
i soldered that chain to a spot on the cavity wall that is connected to the lp ground. i forget where it runs to, bridge or something?

let me ask, how does one ground the paint? put a metal screw into painted cavity and run a wire to the lp ground or output plug ground?

[zirltzn]

May 2, 2014 1:22:46 GMT -5 b4nj0 said:

The screening paint is trying to assimilate a Faraday cage. I believe that it has to be "grounded" to function as a screen. If you are using the screening paint for the pot grounds, then it must be grounded too. The washers have to go (ideally) or be replaced by grounded wires.

e&oe

yes, that was kinda the whole point in painting it. :-) i'm not using the screening paint to ground the pots. the pots are daisy-chained with wires/solder points and that run is connected to the side of the cavity via small screw that is connected to the internal guitar ground or ls paul ground. not sure the correct terminology for that ground. its a bare wire that goes into the inside of the guitar to the bridge or something i think.

the plastic washers ensure the pots now don't touch the paint there.

thanks

[ashcatlt]

There is a screw in the side of the cavity, isn't there?

The thing is, there isn't any actual ground internal to the guitar. The closest you get is the jack shield, which will be connected to something more like real ground via the cable. All of the shielding, all of the signal returns, the bridge wire, and the "grounded lugs" of all of the pots need to connect to the jack shield one way or another. Preferably by as short a path as possible, and without too much redundancy.

[zirltzn]

May 2, 2014 13:33:30 GMT -5 ashcatlt said:

May 1, 2014 13:36:48 GMT -5 b4nj0 said:

Shorted capacitor has to mean no treble roll off.

Are we talking about normal passive pickups with an inductive coil of wire wrapped around a magnet? Is the variable resistance of the T pot parallel to the pickup and output jack? Then reducing that variable resistance absolutely will lower the cutoff frequency of the RL low-pass. Ever heard of tone suck? Ever plugged straight into a line input? The tone cap doesn't really have any effect on the circuit till the variable resistance gets pretty small.

honestly, for me, this is a bit over my head. but the question of variable resistance of the tone pot parallel to the pickup and output jack i think i would like to understand that better. i could have goofed up on the output jack.

[ashcatlt]

May 2, 2014 16:11:56 GMT -5 zirltzn said:

honestly, for me, this is a bit over my head. but the question of variable resistance of the tone pot parallel to the pickup and output jack i think i would like to understand that better. i could have goofed up on the output jack.

Oh, it's just the standard way of wiring a tone control. One end goes to the hot output and one to "ground", which is the same place that the two wires from the pickup go. There may be other things in series and/or parallel in and around, but this is ultimately how it has to work in order to actually work.

Put one probe of your meter on the the pot case and the other on the shield of the jack. Is there any more than a couple ohms resistance? There's your problem.

[zirltzn]

May 2, 2014 16:17:59 GMT -5 ashcatlt said:

May 2, 2014 16:11:56 GMT -5 zirltzn said:

honestly, for me, this is a bit over my head. but the question of variable resistance of the tone pot parallel to the pickup and output jack i think i would like to understand that better. i could have goofed up on the output jack.

Oh, it's just the standard way of wiring a tone control. One end goes to the hot output and one to "ground", which is the same place that the two wires from the pickup go. There may be other things in series and/or parallel in and around, but this is ultimately how it has to work in order to actually work.

Put one probe of your meter on the the pot case and the other on the shield of the jack. Is there any more than a couple ohms resistance? There's your problem.

i resoldered the ground on the output jack to the common ground lug that screws into the wall of the cavity. that screw had a tiny plastic washer. i removed that washer.

both tone controls now function as one would expect with switch on up-mid-dn. COOL!

i did put meter probes where you suggested, there was a little resistance there {if i did it correct}. i don't see any now. and i have tone control now.

thanks all for helping, really appreciate it and my guitar, she does too.

[newey]

Kudos to Ashcatlt for walking Zir through this!

[Deleted]

May 2, 2014 16:11:56 GMT -5 zirltzn said:

May 2, 2014 13:33:30 GMT -5 ashcatlt said:

Are we talking about normal passive pickups with an inductive coil of wire wrapped around a magnet? Is the variable resistance of the T pot parallel to the pickup and output jack? Then reducing that variable resistance absolutely will lower the cutoff frequency of the RL low-pass. Ever heard of tone suck? Ever plugged straight into a line input? The tone cap doesn't really have any effect on the circuit till the variable resistance gets pretty small.

honestly, for me, this is a bit over my head. but the question of variable resistance of the tone pot parallel to the pickup and output jack i think i would like to understand that better. i could have goofed up on the output jack.

oops i am sure this has been asked and answered one million times here and elsewhere but the way i see it in my strat, is that the jack ground has to be connected to the bridge and strings somehow, that's why touching the strings severely reduces buzz/hiss and hum right?
In all my guitars the ground is also connected to the bridge, except an EMG 81/60 guitar in which connecting/disconnecting the bridge has no effect at all.
Also i recall the original GN1, and this massive cap mod, to reduce the possibility of electrical hazard, so surely grounding the strings in the old fashioned way has some danger... (but todays with all all effects and modeling amps, few ppl connect directly to the tube amp, i guess)

so, in effect :
no pup grounding -> no sound
no vol pot grounding -> no vol pot -> still some sound
no tone pot grounding -> no tone control
no bridge/strings grounding -> lots of hum/hiss

a nice guide can be found here :

[zirltzn]

May 6, 2014 3:57:20 GMT -5 @pyrros said:

May 2, 2014 16:11:56 GMT -5 zirltzn said:

honestly, for me, this is a bit over my head. but the question of variable resistance of the tone pot parallel to the pickup and output jack i think i would like to understand that better. i could have goofed up on the output jack.

oops i am sure this has been asked and answered one million times here and elsewhere but the way i see it in my strat, is that the jack ground has to be connected to the bridge and strings somehow, that's why touching the strings severely reduces buzz/hiss and hum right?
In all my guitars the ground is also connected to the bridge, except an EMG 81/60 guitar in which connecting/disconnecting the bridge has no effect at all.
Also i recall the original GN1, and this massive cap mod, to reduce the possibility of electrical hazard, so surely grounding the strings in the old fashioned way has some danger... (but todays with all all effects and modeling amps, few ppl connect directly to the tube amp, i guess)

so, in effect :
no pup grounding -> no sound
no vol pot grounding -> no vol pot -> still some sound
no tone pot grounding -> no tone control
no bridge/strings grounding -> lots of hum/hiss

a nice guide can be found here :

looks my issue was most certainly the "no tone pot grounding". my head almost bled from pounding it on the wall wondering how to fix it and wrap my head around.

really appreciate the links and education on this. got the links in my bookmarks and will visit to readup.

thanks much!

[zirltzn]

May 5, 2014 21:51:02 GMT -5 newey said:

Kudos to Ashcatlt for walking Zir through this!

i ditto!

[ashcatlt]

May 6, 2014 20:29:51 GMT -5 zirltzn said:

May 5, 2014 21:51:02 GMT -5 newey said:

Kudos to Ashcatlt for walking Zir through this!

i ditto!

I mean I'm glad I could help, but I feel like I came across as rather contrary in this thread. Frankly, the dude you got it from answered the question when he suggested a grounding issue. Happy it was an easy fix!

[zirltzn]

May 7, 2014 19:51:33 GMT -5 ashcatlt said:

May 6, 2014 20:29:51 GMT -5 zirltzn said:

i ditto!

I mean I'm glad I could help, but I feel like I came across as rather contrary in this thread. Frankly, the dude you got it from answered the question when he suggested a grounding issue. Happy it was an easy fix!

contrary? no not at all.

and yeah, mr jonesy did mention that. but i tried a few things and couldn't get it to work so i gave up. then it bugged me some more, like with a distortion pedal, and i came back to ol guitarnutz, to try again.

so some tidbits of info on this thread helped. between mr jonesy and you and others we got her working. it does make a difference having the tone knobs working again.

many thanks to all