# Ground Hum



## Milkman (Feb 2, 2006)

I'm wiring up a "Tele" and I have an unusual (for me at least) ground hum.

It almost disappears when I touch the jack or pots, but gets noticeably louder when I touch the switch.

I even tried adding a ground wire from the bridge to the control cavity (shouldn't be needed on a Tele, but...)

No joy.

I've checked for cold solder or loose connections and see nothing obvious.

Any trouble shooting tips? This is the diagram I used. Everything works right. I substituted the tone cap for a 0.22.


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## greco (Jul 15, 2007)

Did you check the wiring at the output jack? "Embarrassing" and simple error but it might be the cause. 
Given that "misery loves company" ..it happened to me recently. There...I admitted it publically.


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## Rollin Hand (Jul 12, 2012)

greco said:


> Did you check the wiring at the output jack? "Embarrassing" and simple error but it might be the cause.
> Given that "misery loves company" ..it happened to me recently. There...I admitted it publically.


Seconded. the worst hum I ever had on a guitar was the result of a bad input jack. The embarrassing part for me was that even though one lug was moving, I never clued in. Replaced the jack and the guitar is quiet as a church mouse now.


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## greco (Jul 15, 2007)

I was tired and in a hurry...wired a new Switchcraft jack backwards.


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## Milkman (Feb 2, 2006)

greco said:


> Did you check the wiring at the output jack? "Embarrassing" and simple error but it might be the cause.
> Given that "misery loves company" ..it happened to me recently. There...I admitted it publically.



Upon your suggestion, yes, I just checked and tip is hot, sleeve is ground. Also, when I touch the jack the hum diminishes (almost disappears) so that area seems normal.

I'm inclined to do the switch over. I think my problem may be there as the hum gets louder when I touch the switch.


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## greco (Jul 15, 2007)

Please let us know what you find. Good Luck!


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## Milkman (Feb 2, 2006)

greco said:


> Please let us know what you find. Good Luck!


Thanks Dave.

I'll re-do the switch. I have an open ground somewhere, but it's not obvious to the eye (just the ear).


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## Milkman (Feb 2, 2006)

One difference between a normal Tele and this one is that there's no steel control plate. The controls are rear mounted.

Also, instead of bending the top leg of the V pot over and soldering it to the pot, I ran a little wire. I'll start with that. I don't see how that would cause this but it's a change point.

It has to be something on the switch.


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## mhammer (Nov 30, 2007)

IN some instances, I see people connect the bridge to ground through a capacitor.


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## greco (Jul 15, 2007)

Milkman said:


> I'll re-do the switch. I have an open ground somewhere, but it's not obvious to the eye (just the ear).


Is the switch grounded?


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## Milkman (Feb 2, 2006)

I just ran a temporary ground wire from the switch housing to the common ground and that seems to have fixed it.

That probably doesn't happen in most Teles because everything is mounted to a steel plate.

I'll try a more permanent soldered ground and maybe also shield the cavity with copper.


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## Milkman (Feb 2, 2006)

greco said:


> Is the switch grounded?


Nope. Ding, ding, ding. That might just be it.


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## DavidP (Mar 7, 2006)

... a DMM is your pal in situations like this -- systematically check every ground connection, working back from the jack... The switch should be automatically grounded to the control plate.


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## greco (Jul 15, 2007)

Milkman said:


> One difference between a normal Tele and this one is that there's no steel control plate.





DavidP said:


> The switch should be automatically grounded to the control plate.


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## Milkman (Feb 2, 2006)

DavidP said:


> ... a DMM is your pal in situations like this -- systematically check every ground connection, working back from the jack... The switch should be automatically grounded to the control plate.


That would be true if there was a control plate.

This guitar has none. I grounded the switch and shielded the cavity. Problem solved.


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## Milkman (Feb 2, 2006)

Milkman said:


> That would be true if there was a control plate.
> 
> This guitar has none. nI grounded the switch. The problem is basically fixed.
> 
> View attachment 372709


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## laristotle (Aug 29, 2019)

Can you post a gut shot?


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## greco (Jul 15, 2007)

Milkman said:


> I grounded the switch and shielded the cavity. Problem solved.


CONGRATS! 

Looks great!


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## Milkman (Feb 2, 2006)

laristotle said:


> Can you post a gut shot?


Not pretty, but I've seen worse.


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## Milkman (Feb 2, 2006)

laristotle said:


> Can you post a gut shot?


Sorry, not much to see. It's working as it should now.


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## laristotle (Aug 29, 2019)

Milkman said:


> Not pretty, but I've seen worse.


😒
I had to ask. lol


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## knight_yyz (Mar 14, 2015)

I've mentioned this to you before. Sometimes it happens sometimes it doesn't. You should not ground the tele pots together with a wire if you have a metal control plate. It can sometimes introduce ground loop hum. If you look at an LP wiring schematic the 4 pots are grounded but the loop is not closed. 3 wires for 4 pots. If you added a 4th wire there is a good chance for ground loop hum. 
On the tele the metal plate grounds the pots together. Adding the wire closes the loop... That's why I always ask you guys, rear route or metal control plate... Oh shielding does the same thing as the plate. So again copper or conductive paint, no wire between pots required


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## Milkman (Feb 2, 2006)

knight_yyz said:


> I've mentioned this to you before. Sometimes it happens sometimes it doesn't. You should not ground the tele pots together with a wire if you have a metal control plate. It can sometimes introduce ground loop hum. If you look at an LP wiring schematic the 4 pots are grounded but the loop is not closed. 3 wires for 4 pots. If you added a 4th wire there is a good chance for ground loop hum.
> On the tele the metal plate grounds the pots together. Adding the wire closes the loop... That's why I always ask you guys, rear route or metal control plate... Oh shielding does the same thing as the plate. So again copper or conductive paint, no wire between pots required



There's no control plate on this one (rear mounted pots and switch).

Adding the copper shielding didn't solve it or make it worse.

The issue seems to have been resolved by grounding the switch.


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## HeavyMetalDan (Oct 5, 2016)

I found some Flux makes soldering to the pots way easier for a better ground


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## Milkman (Feb 2, 2006)

HeavyMetalDan said:


> I found some Flux makes soldering to the pots way easier for a better ground


Good idea.

I was looking for some while wiring this one up but didn't find any. I'll be picking some up for sure. I was having trouble getting the ground wire to solder to the switch and flux would have helped.


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## mhammer (Nov 30, 2007)

There are two aspects to achieving a good solder joint. One is certainly the "receptiveness" of the metal to solder, and liquid flux can help with that, as can a little bit of surface scraping with a blade. A $10 bottle of the stuff, doled out with toothpicks and Q-tips, as needed, can last you a lifetime. The other aspect is the contacts' dual personality as "contact" and as "heat sink". Large metal surfaces/objects soak up and distribute heat from the iron tip, which prevents the solder and contact from reaching the necessary temperature to flow onto the contact surface. In such instances, while I am reluctant to use it in such spaces, the classic soldering "gun", that resembles a pistol, with the soldering tip a long bent piece of of thick copper, easily achieves the required temperature. So can the sort of soldering irons one might use for plumbing repairs, but those tips can be cumbersome.


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## Milkman (Feb 2, 2006)

mhammer said:


> There are two aspects to achieving a good solder joint. One is certainly the "receptiveness" of the metal to solder, and liquid flux can help with that, as can a little bit of surface scraping with a blade. A $10 bottle of the stuff, doled out with toothpicks and Q-tips, as needed, can last you a lifetime. The other aspect is the contacts' dual personality as "contact" and as "heat sink". Large metal surfaces/objects soak up and distribute heat from the iron tip, which prevents the solder and contact from reaching the necessary temperature to flow onto the contact surface. In such instances, while I am reluctant to use it in such spaces, the classic soldering "gun", that resembles a pistol, with the soldering tip a long bent piece of of thick copper, easily achieves the required temperature. So can the sort of soldering irons one might use for plumbing repairs, but those tips can be cumbersome.


All true and all helpful.

When soldering to the backs of pots or even more so to a trem claw, you often need more heat than a nice pencil typle soldering iron will provide. I have a dual power weller gun for such purposes, but I often try to tough it out and use the smaller iron.

Sometimes just cleaning the surfaces with solvent helps.


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## mhammer (Nov 30, 2007)

The truly irritating case is when the solder_* looks*_ like it has a formed a nice joint, and then the "nice" solder blob just pulls right off with the slightest pressure. I generally scrape a bit of the back of the pot to reveal what's underneath.


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## Milkman (Feb 2, 2006)

mhammer said:


> The truly irritating case is when the solder_* looks*_ like it has a formed a nice joint, and then the "nice" solder blob just pulls right off with the slightest pressure. I generally scrape a bit of the back of the pot to reveal what's underneath.


Yeah that does suck because typically that happens after you have been struggling with a connection and you think you just finally nailed it......


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## Paul Running (Apr 12, 2020)

A solderabilty chart
The high-lighted yellow elements are the metals that I choose for allowing this to be enjoyable for me. I believe that most electronic components are terminated to one or maybe all of these elements. I hated soldering at first, until I discovered the effectiveness of a fully activated flux. A warning though, if you use a 1544/88 (green high-light), clean it within a few minutes...it is lightly corrosive to certain metals...it's easier to remove when warm with a mild solvent, for hardy components, I am not afraid to use varsol dipped swabs...I usually purchase them (the swabs) at Princess Auto when they are on sale (PA, a cool store to browse in the surplus section as there is always something interesting). Stay away from the red crossed-out regions...not a friendly neighbourhood.


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## laristotle (Aug 29, 2019)

mhammer said:


> the solder_* looks*_ like it has a formed a nice joint, and then the "nice" solder blob just pulls right off with the slightest pressure


I found that same problem with the volume tab ground on my Firebird. From the factory!? 
Even the cap on the tone pot wasn't done.
But, it helped me buy it for a reduced price.


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## Paul Running (Apr 12, 2020)

laristotle said:


> Even the cap on the tone pot wasn't done.


Back in my day, the inspector would take all the heat on that one and it would all trickle down from there into a funnel of crap that would sit on your lap...the person who forgot to apply solder to that joint.


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## Milkman (Feb 2, 2006)

Shaky hands and poor eyesight are not advantages in this context.


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## Paul Running (Apr 12, 2020)

Yeah, usually I can solve the eye issue with a good pair of glasses however, the shaky hand is much more challenging...cannabis doesn't always work for me on this one.


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## mhammer (Nov 30, 2007)

Soldering to the plastic dust caps on the back of pots is NOT recommended, unless you REALLY like the chemical smells produced. The solder looks like it sticks, which is good I suppose, but there is poor continuity between the plastic cap and the back of the pot.


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## knight_yyz (Mar 14, 2015)

My best friends when I make harnesses for you guys... Liquid flux with a needle tipped bottle.


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