still getting hum from the humbuckers

[Snoogles]

so i've wired my guitar with 2 humbuckers and the jimmy page wiring.
have everything grounded and shielded.
yet on a medium gain setting i still get hum which is cancelled (or at least reduced) when i touch anything metal on the guitar. as well as when i grab the cable jack housing which is plastic

and here's a twist:
when i put my hand up to the rear cavity cover, i get INCREASED hum

is this normal for humbuckers?

 

[Chocklit_Thunda]

Re: still getting hum from the humbuckers

You may need to check your solder joints again. It could be a grounding issue.
Basically check all your connections and also the bridge ground wire.

 

[Snoogles]

Re: still getting hum from the humbuckers

You may need to check your solder joints again. It could be a grounding issue.
Basically check all your connections and also the bridge ground wire.

just checked all of the ground connections with a multimeter. everything seems to be hooked up

my other humbucker guitar doesn't have this problem at all. and the only real difference is that the one that's giving me problems has hybrid pickups (ie: bridge pickup has north coil=8.5k south coil=5.4).

i don't want to have to re-do all of the wiring again

 

[BlueTalon]

Re: still getting hum from the humbuckers

You shouldn't have to re-do all of the wiring, but you might have to go back and re-shield it and re-ground it. Is the rear cavity cover shielded? That's the first thing I would check. I use self-adhesive copper foil (the stuff is pretty inexpensive from China on ebay). If it is shielded, then make sure it is connected to the cavity shielding when it's in place. If any part of the shielding is isolated from ground, then instead of protecting the guitar from EM interference, it can act like an antenna.

From the front of the guitar, can you check the continuity between the bridge and the inside of the pickup routes and get close to 0 ohms? Are the wire channels between cavities shielded? Or are the wires themselves shielded?

 

[Snoogles]

Re: still getting hum from the humbuckers

You shouldn't have to re-do all of the wiring, but you might have to go back and re-shield it and re-ground it. Is the rear cavity cover shielded? That's the first thing I would check. I use self-adhesive copper foil (the stuff is pretty inexpensive from China on ebay). If it is shielded, then make sure it is connected to the cavity shielding when it's in place. If any part of the shielding is isolated from ground, then instead of protecting the guitar from EM interference, it can act like an antenna.

From the front of the guitar, can you check the continuity between the bridge and the inside of the pickup routes and get close to 0 ohms? Are the wire channels between cavities shielded? Or are the wires themselves shielded?

i put the coper tape on the cavity cover.
i have my doubts about the shielding paint inside the cavity. when i test my other guitar's shielding paint with a multimeter i get some kind of reading where ever i touch the probes. not so in this guitar's electronics cavity.
i think i might strip it out and shield with the copper tape. freak'n PITA though

i never thought to check the connection between the bridge and the pickup route. the pickup's wires are shielded and grounded (duncan 4-conductor)

 

[uOpt]

Re: still getting hum from the humbuckers

Looks like the shield on the cavity cover goes to hot. Might even work if hot is just touching the plastic but since you say everything is shielded you cannot possible have just a plastic cover.

 

[Snoogles]

Re: still getting hum from the humbuckers

Looks like the shield on the cavity cover goes to hot. Might even work if hot is just touching the plastic but since you say everything is shielded you cannot possible have just a plastic cover.

not exactly sure what you're saying
there really isn't any difference in the humming whether the cover is on or off. but its not a plastic cover. its a wood cover with copper tape shielding. and i don't think the shielding is touching anything else except the cavity paint.

however, i did recently realize that my laptop computer greatly adds to the humming. especially with a youtube video running, and when i'm using the mouse pad.

 

[uOpt]

Re: still getting hum from the humbuckers

not exactly sure what you're saying
there really isn't any difference in the humming whether the cover is on or off. but its not a plastic cover. its a wood cover with copper tape shielding. and i don't think the shielding is touching anything else except the cavity paint.

however, i did recently realize that my laptop computer greatly adds to the humming. especially with a youtube video running, and when i'm using the mouse pad.

The back cover for the electronics cavity is wood? In any case if touching it increases noise of some kind it is somehow semi-connected to a hot wire.

 

[Snoogles]

Re: still getting hum from the humbuckers

The back cover for the electronics cavity is wood? In any case if touching it increases noise of some kind it is somehow semi-connected to a hot wire.

all i have to do is pass my hand over the rear of the guitar where the controls are (whether the cover is in place or not), without touching anything, and the hum increases. hum also increases when i touch the hot wire going from the switch to the hot output on the cable jack.

i think its the shielding paint, cuz its only in a very few areas that i get a reading on the multimeter. so if there's sheilding paint that's not connected to ground, as BlueTalon says, it will act like an antenna.
question is, do i need to strip out the current paint, or can i just paint over it (copper tape wont adhere)? i think i need to strip it out.

 

[AlexR]

Re: still getting hum from the humbuckers

There's more hum inherent in the hybrid pickup, or anything with a large coil strength offset. I'd say that there will be another factor involved with regard to some of the other effects. You'll have a ground loop or similar created with the touching of various parts......although you seem to be on the right track with the shielding - Maybe its not connecting and there are areas of separate grounds

 

[uOpt]

Re: still getting hum from the humbuckers

all i have to do is pass my hand over the rear of the guitar where the controls are (whether the cover is in place or not), without touching anything, and the hum increases. hum also increases when i touch the hot wire going from the switch to the hot output on the cable jack.

i think its the shielding paint, cuz its only in a very few areas that i get a reading on the multimeter. so if there's sheilding paint that's not connected to ground, as BlueTalon says, it will act like an antenna.
question is, do i need to strip out the current paint, or can i just paint over it (copper tape wont adhere)? i think i need to strip it out.

You are absolutely sure the copper foil on the electronics cover is grounded?

 

[octavedoctor]

Re: still getting hum from the humbuckers

You are absolutely sure the copper foil on the electronics cover is grounded?

I'm with uOpt on this. I think that you are getting inductive hum, perhaps because the foil on the control cover plate is not connected to the rest of the screen and there is a signal wire touching the foil. The signal core doesn't have to be touching it, you'll get capacitative coupling even if the insulation is touching the foil if the foil isn't earthed.

Also, have you remembered to screen the socket cavity and the switch cavity? many people forget about this but for screening to be effective it has to be contiguous, comprehensive and grounded.

 

[octavedoctor]

Re: still getting hum from the humbuckers

all i have to do is pass my hand over the rear of the guitar where the controls are (whether the cover is in place or not), without touching anything, and the hum increases. hum also increases when i touch the hot wire going from the switch to the hot output on the cable jack.

i think its the shielding paint, cuz its only in a very few areas that i get a reading on the multimeter. so if there's sheilding paint that's not connected to ground, as BlueTalon says, it will act like an antenna.
question is, do i need to strip out the current paint, or can i just paint over it (copper tape wont adhere)? i think i need to strip it out.

You don't need to strip it, just paint over it and make sure that you paint everywhere.

 

[Snoogles]

Re: still getting hum from the humbuckers

I'm with uOpt on this. I think that you are getting inductive hum, perhaps because the foil on the control cover plate is not connected to the rest of the screen and there is a signal wire touching the foil. The signal core doesn't have to be touching it, you'll get capacitative coupling even if the insulation is touching the foil if the foil isn't earthed.

Also, have you remembered to screen the socket cavity and the switch cavity? many people forget about this but for screening to be effective it has to be contiguous, comprehensive and grounded.

i would imagine that the foil on the cover isn't grounded, since the shielding paint in the cavity doesn't show a reading when multimetered. so the foil isn't really making contact with anything.
but there's no difference in hum whether the cover is on or off.

i think i'll re-paint the cavities
thanks for all the info

 

[Snoogles]

Re: still getting hum from the humbuckers

i think i figured out the problem. i've always used regular hook up wire leading to the hot output jack terminal. i'm going to replace it with shielded wire this afternoon.

 

[MrTondo]

Re: still getting hum from the humbuckers

Sounds like that could very well be it. Especially when noticing extra hum near a pc or other radiation sources unshielded wires or parts are a usual suspect.

I've never heard of hybrid pickups causing extra hum. Usually it is either bad shielding of signal wires or ground loops when you hear too much hum.

 

[Snoogles]

Re: still getting hum from the humbuckers

that seemed to solve the issue.