Humming like guitar isn't plugged in

[jmaf]

Boooooo....

He's missing a ground. Get it?! Get it!?

[Danelectron]

He's missing a ground. Get it?! Get it!?

Yep, but I'm punned out now.

[Phil66]

Ok ok ok, I'm missing a ground but where??? It is wired like this Wiring Diagram the guitar tech can't find a missing ground anywhere, it didn't do it with the standard Epiphone pickups but I guess they were low output, none of my other guitars do it. Think I'll take it to another shop for a 2nd opinion.

[Danelectron]

I think big_teee may be on to something. If you are getting EMF interference, flipping off breakers one at a time will kill the source of it provided it isn't something on the same circuit. It seems if the tech couldn't make it hum in the shop there must be something happening at your location. Interesting.

[Phil66]

It was there in the shop but very very quiet, personally I don't think it should be there at all but they say it is an acceptable level.

I'll have to wait for the right day to start flipping switches.

Phil

[Phil66]

They could hear it at the shop but it was very quiet and acceptable even though we agree it shouldn't be there at all. The only solution is to put the old pickups back on which I don't want to do.

Phil

[Danelectron]

acceptable level

Most amp/guitar setups exhibit some hum and I agree there are acceptable levels, but if you had no hum before the new pickups and the techs can't find any wiring issues, that narrows it down to the pickups or noise at the homestead. Is the hum evident on each pickup? Is the hum level obviously louder at your home or subtly different? I'm only asking that because depending on how busy the shop is, there will be significantly more background noise (Kids demoing drums, etc.) making it seem as though the problem is more drastic at home. Would the shop be willing to swap in some different pickups? It wasn't Guitar Center was it? If it is the pickups making the hum and the hum is at undesirable levels, would you be happier with the old ones? I reread your intro post and I don't believe it is an EMF noise issue.

[jmaf]

If you unplug the guitar from the amp and the hum goes away, the it's the guitar + cable + environment AND/OR the input to V1(rare cases). I guess that's obvious, but if there's any question whether the hum is coming from in or out of the amp, that's your simplest test.

[Phil66]

If I unplug the guitar from the lead but leave the lead in the amp it gives me the same hum as when the volume is down and the tone up.

[Phil66]

Ok, I've been studying the schematic again, Wiring Diagram please have patience, I go wonky eyed looking at these things and I may have spotted something that I missed before, I don't understand if these differences will make a difference. I have noticed that the cable from the centre tab of the 3 way switch is soldered to the input, it has two wires in it and there is one for each contact.
On the schematic the ground wire from the bridge is soldered to the bridge tone and linked to the neck tone and the ground on the jack, on my guitar it is soldered to the neck tone and linked to the bridge and that's it.
I also notice that the capacitors are soldered to the left hand tabs of the tone pots not the middle as in the schematic, I would think this is how it left the factory as the guy that fitted the pickups had no need to change this.
The yellow wire from the pickup selector for the bridge pup is solder to the back of the vol pot and the right hand tab, the is a linking wire from this to back of the tone pot and the middle tab on the tone pot.
The red wire from the selector for the neck pup is soldered to the back and the right tab of the vol pot and the conecting wire is soldered to the back and the middle of the tone pot.

As I say, I don't know enough to say whether this would make a difference or not, I need "The Idiots Guide To Guitar Wiring"

Cheers

Phil

[big_teee]

Can you confirm the right terminal from the rear of each vol. pot.
That terminal should be grounded.
Is the right Volume Terminal on each Vol. Pot connected to ground, that would be the back of the Vol. Pot?
That's where the star ground comes. That's what makes it quiet when you turn the volume down.
No ground on terminal 3, it will not be quiet when you back off the volume.
Terry

[Phil66]

Hello again, OK I've made a schematic, please excuse the amateurishness of it. The line with the squiggle is an error, it was the last one I was drawing and I cocked up and didn't want to do it all again.
Please have a look and let me know the easiest solution.


Uploaded with ImageShack.us

Cheers

Phil

[big_teee]

Hello again, OK I've made a schematic, please excuse the amateurishness of it. The line with the squiggle is an error, it was the last one I was drawing and I cocked up and didn't want to do it all again.
Please have a look and let me know the easiest solution.


Uploaded with ImageShack.us

Cheers

Phil

I think I see your problem.
On the 2 Volume Pots the middle wire(Pot Wiper) on each Pot should wire to the switch.
The Black wire of each pickup should wire to side Terminal not Grounded.
The other side terminal should be grounded, like you show in your diagram.
The switch wire has to be in the middle.
Fix the wiring and it will work properly I bet!
Compare to the diagram below.
Good Luck,
Terry

[Phil66]

Woooohooooooo,

We have progress, sort of. Ok I swapped the blacks and whites on the vol pots (there was two whites and one black on each). That has completely stopped the humming problem. The blacks were on the middle tab and the whites on the outer tab BUT the whites were linked to the middle tab on the tone pots.
I have created another problem though. I don't get any sound in the middle position unless I have BOTH volumes at the same setting. I have not changed the wiring to the input jack yet but surely that can't be what is causing this?
Any ideas what this could be? I think it might be blindingly obvious to you.
I'll sort it if it kills me ;o)
Phil

[big_teee]

Your correct, you cant turn either volume off, in the middle switch posistion.
The reason, is because when you roll off the volume you are grounding out the input jack.
So both volumes have to be used together in the middle posistion.
I set the volume of neck pot in neck posistion.
Then I do the same with the bridge Volume.
Then when you switch to middle each pickup should be putting out similar output.
The jumper on the tone, will work wired either way. The way you had it is fine.
I like the way Seymour D. Does it. If you follow there plan you can't go wrong.
Good Luck,
And Thanks for hanging in there.
Later,
Terry