Guitar electronics issue??

[elenore19]

Alright, so I played the other day with some people...Alright, there's that.

My amp was having more hum than usual. So whenever I put my hand on any of my knobs or switch..(I have 2 knobs, 1 switch...that is too sexual to not say anything....The hum would go away instantly. Or if I turned my volume knob all the way down.


So any suggestions? theories?

[cakewalkKaKed]

sounds like bad earth ... good fun tracking it down though !!!

[eyema_believer]

Yep.... did you plug your amp into an outlet different than you normally do? That was probably it.

[elenore19]

I did. And it does the same thing where I usually plug it in as well. So bad ground in Both places? I just didn't realize it where I usually plug in because I don't turn my amp up that loud to realize it. But it does it.

So yeah.

Any other ideas?

[eyema_believer]

Originally Posted by elenore19

I did. And it does the same thing where I usually plug it in as well. So bad ground in Both places? I just didn't realize it where I usually plug in because I don't turn my amp up that loud to realize it. But it does it.

So yeah.

Any other ideas?

Try plugging in another guitar and cord, eliminate those first, since that would be easiest. Your problem is almost certainly a bad ground.... just hope it's not your new amp.

[mshilarious]

Originally Posted by elenore19

Any other ideas?

Yes. It's not a bad ground. It's induced interference from some external source. Find the source by turning crap off until it goes away.

[elenore19]

Originally Posted by eyema_believer

Try plugging in another guitar and cord, eliminate those first, since that would be easiest. Your problem is almost certainly a bad ground.... just hope it's not your new amp.

Yeah, you'd think...
I only have one guitar.
I only have one power cable.

The amp isn't new. Well I've had it for like 9 months.

Originally Posted by mshilarious

Yes. It's not a bad ground. It's induced interference from some external source. Find the source by turning crap off until it goes away.

Yeah, I figure it's probably my guitar. But what would it be?

[Fusioninspace]

Hmmm, interesting. Some other random thoughts:

- Cell phones off vs on
- fluorescent lights?
- A PC nearby
- Humid day - floor slightly damp?
- Did you do any guitar setup (change strings/etc)?
- Someone else have new gear?
- Electrical work done on the facility?
- Microwave added to the circuit somewhere?
- Try someone else's cable or spend $5 for a cheap cable from RatShack just to do a test with
- If it has a trem with springs/claw: re-solder the ground to claw connection. I've seen a bunch of those with a "cold solder" joint and I'm surprised they didn't just pop off by looking at them.

But you didn't mention - single/humbucker?

[elenore19]

Originally Posted by Fusioninspace

Hmmm, interesting. Some other random thoughts:

- Cell phones off vs on
- fluorescent lights?
- A PC nearby
- Humid day - floor slightly damp?
- Did you do any guitar setup (change strings/etc)?
- Someone else have new gear?
- Electrical work done on the facility?
- Microwave added to the circuit somewhere?
- Try someone else's cable or spend $5 for a cheap cable from RatShack just to do a test with
- If it has a trem with springs/claw: re-solder the ground to claw connection. I've seen a bunch of those with a "cold solder" joint and I'm surprised they didn't just pop off by looking at them.

But you didn't mention - single/humbucker?

Humbucker/Single.
A seymour duncan humbucker in the bridge, and then a P90 in humbucker form in the neck position.

I think this problem has been there for a long while, I just haven't really payed attention to it. Not sure how long. So that doesn't really help me much. I figure it's the wiring job because I did it myself when I upgraded the pups. I'll try out some things though and get back to ya.

[Light]

Sounds like it is probably normal, and you were just in a noisier environment than you are used to.



Light

"Cowards can never be moral."
M.K. Gandhi

[elenore19]

Originally Posted by Light

Sounds like it is probably normal, and you were just in a noisier environment than you are used to.



Light

"Cowards can never be moral."
M.K. Gandhi

I really don't think so though. It happens most of the time, wherever I'm plugged in.

[Milnoque]

If there were a grounding problem it could be with your house wiring, especially if it is an older home.

Does the problem exist when nothing is plugged into the amp?

Does touching the strings make it go away when the guitar is plugged in?

[Gear_Junky]

shielding, anyone?

all passive pickups have more (or less) "noise" (60-cycle hum) that they pick up from the surrounding interference. humbuckers eliminate most of it (if properly wired) in the dual-coil mode (but not in single).

touching any grounded part on the guitar (strings/bridge/controls) GROUNDS the player (who is the biggest antenna near the guitar magnifying the interference). that's with correct wiring.

shielding the cavity (and for me, pickups, i love those metal covers, they're not just pretty, they're shields, dontcha know ) may help reduce the hum quite a bit. My Dream 180's are almost equally quiet in single-coil mode as they are in dual.

then again, areas with more interference will give you more hum than areas with less interference, regardless of shielding.

I am not a "pro", so if I'm wrong or missed something, I don't mind standing corrected. But that's been my experience.

[Anfontan]

Maybe harmonics from a cell phone tower, maybe? Those towers are popping up all over the place these days....
There are new signals being broadcast on frequencies all over-it could be the problem.

[elenore19]

Originally Posted by Milnoque

If there were a grounding problem it could be with your house wiring, especially if it is an older home.

Does the problem exist when nothing is plugged into the amp?

Does touching the strings make it go away when the guitar is plugged in?

Touching the strings does nothing. Has to be a knob, or the metal part on the cable, or the metal part of the switch. Also touching any metallic part on the pups.

Originally Posted by Gear_Junky

shielding, anyone?

all passive pickups have more (or less) "noise" (60-cycle hum) that they pick up from the surrounding interference. humbuckers eliminate most of it (if properly wired) in the dual-coil mode (but not in single).

touching any grounded part on the guitar (strings/bridge/controls) GROUNDS the player (who is the biggest antenna near the guitar magnifying the interference). that's with correct wiring.

shielding the cavity (and for me, pickups, i love those metal covers, they're not just pretty, they're shields, dontcha know ) may help reduce the hum quite a bit. My Dream 180's are almost equally quiet in single-coil mode as they are in dual.

then again, areas with more interference will give you more hum than areas with less interference, regardless of shielding.

I am not a "pro", so if I'm wrong or missed something, I don't mind standing corrected. But that's been my experience.

Touching the strings doesn't do anything for the hum. As mentioned above.
Where would I go about looking for these shields?

[antichef]

When you soldered the ground wires to the back of the pot(s) (assuming you did it that way), how good of a connection did you make? I've been doing my own electronics for a few years now, and for some reason I always had the hardest time making that solder joint. As my skills have (slowly) improved, I've been able to reduce/eliminate hum in some earlier masterpieces of mine by solder-sucking up the mess that I made and starting over.

[Gear_Junky]

Originally Posted by elenore19

Touching the strings does nothing

sounds like somebody forgot to ground the bridge

[elenore19]

Originally Posted by antichef

When you soldered the ground wires to the back of the pot(s) (assuming you did it that way), how good of a connection did you make? I've been doing my own electronics for a few years now, and for some reason I always had the hardest time making that solder joint. As my skills have (slowly) improved, I've been able to reduce/eliminate hum in some earlier masterpieces of mine by solder-sucking up the mess that I made and starting over.

I have no idea. It has been hmm...I'd say 2 years since I've upgraded the pups on this guitar. But could that be the problem? I don't have any type of soldering device here at school with me, but I can definitely attempt to fix it this weekend when I go home. I don't remember really doing anything with soldering against the pots...but maybe I don't know what pots are...
I just soldered the humbuckers to the switch, I believe. But you'd know better than me.

[e-man]

gear_junky hit it i think.

sounds like the ground to the bridge has been interrupted. check for the wire that runs to the bridge and make sure its got a good connection at the ground.

later...

[arcaxis]

Below is a pic of my Epi SG with the back cover plate removed. The areas circled in green are the grounding points for the shield wires and are all tied together. The pots are the four devices in the center with the three connection points on each. Yours should be similar.

Have you lately started playing with a setting on your amp that has more gain than before? This would make any hum present more noticable.

The yellow thingy is a testing device to check correct wiring of an outlet. It will tell you if an outlet is not grounded correctly or other problems. Not too expensive at Radio Shack, Home Depot, etc. If you've got an old house the grounding could be buggered up.

Does the orientation of the guitar change the hum? Turning left, right, up, or down. If it changes, the hum might from something in the room.

Does the cavity cover have foil on it and does it look like it will make a good connection to a ground point when in place? When you touch the controls, your body then becomes the ground shield for the back of the guitar and could diminish the hum. The shield paint in the left of the picture is what makes this connection in this SG. A piece of foil in the cavity may rest on the edge to make this connection.

[muttley600]

Originally Posted by e-man

gear_junky hit it i think.

sounds like the ground to the bridge has been interrupted. check for the wire that runs to the bridge and make sure its got a good connection at the ground.

later...

My money is on antichef

[elenore19]

Originally Posted by arcaxis

Below is a pic of my Epi SG with the back cover plate removed. The areas circled in green are the grounding points for the shield wires and are all tied together. The pots are the four devices in the center with the three connection points on each. Yours should be similar.

Have you lately started playing with a setting on your amp that has more gain than before? This would make any hum present more noticable.

The yellow thingy is a testing device to check correct wiring of an outlet. It will tell you if an outlet is not grounded correctly or other problems. Not too expensive at Radio Shack, Home Depot, etc. If you've got an old house the grounding could be buggered up.

Does the orientation of the guitar change the hum? Turning left, right, up, or down. If it changes, the hum might from something in the room.

Does the cavity cover have foil on it and does it look like it will make a good connection to a ground point when in place? When you touch the controls, your body then becomes the ground shield for the back of the guitar and could diminish the hum. The shield paint in the left of the picture is what makes this connection in this SG. A piece of foil in the cavity may rest on the edge to make this connection.

Wow, fantastic! I'll definitely have a look. My guitar only has one volume and one tone. So only 2 pots. But it still should be similar, right? Yeah. Alright. I'll hopefully figure this out.

Thanks man!

[Gear_Junky]

i believe that when you have shielding, you should NOT connect backs of pots with ground wires. they should be grounded by the shielding (just by virtue of touching it) and they are. these wires are ground loops now. may or may not be a problem (noise-wise) but certainly unnecessary. It's all described in the articles on shielding. If your shielding material (foil or paint) is not itself grounded (by soldering a wire to the foil or to a screw/washer, which is driven into the wood so as to touch the shield) then it does no shielding.

Originally Posted by arcaxis

Below is a pic of my Epi SG with the back cover plate removed. The areas circled in green are the grounding points for the shield wires and are all tied together. The pots are the four devices in the center with the three connection points on each. Yours should be similar.

Have you lately started playing with a setting on your amp that has more gain than before? This would make any hum present more noticable.

The yellow thingy is a testing device to check correct wiring of an outlet. It will tell you if an outlet is not grounded correctly or other problems. Not too expensive at Radio Shack, Home Depot, etc. If you've got an old house the grounding could be buggered up.

Does the orientation of the guitar change the hum? Turning left, right, up, or down. If it changes, the hum might from something in the room.

Does the cavity cover have foil on it and does it look like it will make a good connection to a ground point when in place? When you touch the controls, your body then becomes the ground shield for the back of the guitar and could diminish the hum. The shield paint in the left of the picture is what makes this connection in this SG. A piece of foil in the cavity may rest on the edge to make this connection.

[arcaxis]

Originally Posted by Gear_Junky

i believe that when you have shielding, you should NOT connect backs of pots with ground wires. they should be grounded by the shielding (just by virtue of touching it) and they are. these wires are ground loops now. may or may not be a problem (noise-wise) but certainly unnecessary. It's all described in the articles on shielding. If your shielding material (foil or paint) is not itself grounded (by soldering a wire to the foil or to a screw/washer, which is driven into the wood so as to touch the shield) then it does no shielding.

I believe most any guitar I've had has had the backs of the pots grounded when there was also cavity shielding. In the case of this Epiphone it's the pots that actually make the shield ground connection to the shielding paint in the cavity. Maybe not a great way to do it, but cheap and easy.

Some Google hits showing pot grounding...

http://www.stewmac.com/cgi-bin/hazel...eeinfo/fi.html

http://alexplorer.net/guitar/basics/grounding.html

http://www.fretnotguitarrepair.com/E...nicsRepair.htm

http://www.guitarnucleus.com/wiring.html

[Gear_Junky]

Originally Posted by arcaxis

I believe most any guitar I've had has had the backs of the pots grounded when there was also cavity shielding.

yeah, i know what you mean. they also often put foil on cavity covers, but that foil is not connected to anything. a bridge to nowhere.

In the case of this Epiphone it's the pots that actually make the shield ground connection to the shielding paint in the cavity. Maybe not a great way to do it, but cheap and easy.

oh, but it is the right way - any metal part of the pot (except lugs) is ground. That's why you don't need those black (in your case blue and red) wires that connect pots and then go to ground. I think.

See here:

http://www.guitarnuts.com/wiring/shielding/shield3.php

It's for a strat, but logic can easily be applied to any other guitar. I don't own strats and I was able to use it no prob.

Here's a pic he uses:



the grey background represents the shield, which is a conductor, it grounds everything that touches it.

That article is VERY well written and illustrated and gets results. I've done this to a friend's strat, a bass and my own les-paul type guitar. Worth a read.