Ground/Shielding issue? I have continuity but still getting hum

[CadenGuitars]

Hi All,

I have a guitar that has an issue that appears to be a ground issue (hum sound that goes away when touching strings/trem claw/any metal part), but I have checked all the components and am getting continuity from all of them (jack, pots, trem, bridge, strings & tuners).

The only other thing I can see is that the control cavity is not shielded. Before I go through all the trouble to pull out all the electronics to shield the cavity, I was wondering if there is anything else that could be the culprit that I should troubleshoot before shielding? Is the noise described above a product of not having shielding as I thought that was more for interference from outside electrical sources, which I'd assume touching the strings would not solve.

Any and all help is appreciated. FWIW it's a rear-routed JEM style custom build with floyd rose bridge.

 

[MaxOfMetal]

Have you checked the ground connection further downstream?

 

[CadenGuitars]

Hey Max,

Not sure what you mean further downstream, do you mean after the signal has left the guitar or? I have checked the guitar on two different amps, and when I plug in any of my other guitars on those amps I am not getting the issue, only on this particular one which leads me to believe the issue is with the guitar itself.

 

[MaxOfMetal]

Hey Max,

Not sure what you mean further downstream, do you mean after the signal has left the guitar or? I have checked the guitar on two different amps, and when I plug in any of my other guitars on those amps I am not getting the issue, only on this particular one which leads me to believe the issue is with the guitar itself.

Yeah, I meant outside of the guitar. But it sounds like you've already checked that.

You have a bad ground somewhere. For cases like this I've always found it faster and easier to just rewire the guitar. Hunting for gremlins like this is a pain, but a rewire is far less of a pain.

 

[Paradox916]

can you take a pic of the control cavity so we can see what you are working with?

 

[CadenGuitars]

Yeah, I meant outside of the guitar. But it sounds like you've already checked that.

You have a bad ground somewhere. For cases like this I've always found it faster and easier to just rewire the guitar. Hunting for gremlins like this is a pain, but a rewire is far less of a pain.

I see, may have to come to that. So then it is correct that this type of issue has nothing to do with shielding and it will be a ground issue somewhere, right?

can you take a pic of the control cavity so we can see what you are working with?

 

[CadenGuitars]

So I have been troubleshooting and came across this video from dylantalkstone where at the 5:20 mark describes the issue I’m having and says it’s completely normal.



However my question is why don’t any of my other guitars do the same thing? Does this point to a shielding issue? FWIW the buzz is loudest in positions 1 and 5 (full Humbuckers), quietest in 2 and 4 (humbucker split with single cool in the middle), and medium buzz but still pretty quiet in position 3 on the single coil by itself.

 

[ToRNOuTLaW]

Have you made sure that the cable is really plugged all the way in? Sometimes the spring in the socket is bend and doesn't fully make contact (with the right part of the plug).

 

[Mike]

Try moving in different positions around your room, face away from the amp, get as far away from the amps transformer as you can. If you notice the noise reduces, it's an emi issue.

Shielding the electronics cavity will help some (paint or copper tape. I like the XGP paint personally). Make sure there's some shielding (copper/foil tape) on the cavity cover too. Do NOT shield the pickup cavities. It absolutely draws in more noise. I have done extensive experiments on this bullshit and have reduced noise on multiple guitars by sanding off shielding paint that came in pickup cavities. Don't care if you run ground wires from the pickup cavity to the control cavity. Doesn't work. Shielding/conductive paint in pickup cavities is an incomplete faraday cage that simply draws in more interference that goes straight through the pickup. That's my story and I'm sticking to it.

 

[Paradox916]

It’s hard to see but the solder joints from what I can tell look ok, so you have continuity from the jack housing (sleeve not tip) to the back of a pot housing? That would be the first thing I would check, since the jack sees the most punishment and that ground wire is usually the first to give up the ghost… but shielding the control cavity isn’t a bad Idea, it will also let you get in there and start looking you might find an issue you didn’t otherwise see with out moving wires and components, fraying wires cold solder joints ect…

 

[DoctorStoner]

The few times I've had this issue, it was the guitar's input jack. I just installed a good new one. It's quick and cheap.

Another is the selector going bad, but I've found that comes with intermittent volume/signal drop as well.

 

[elkoki]

Do you use those noiseless Floyd Rose springs ? It appears you are from what I can make out ? I ask because some of them are covered in polymer which is supposed to dampen spring noise but since the springs are covered all over with that stuff they prevent the bridge from grounding . Just an idea .. It could be the electronics but I just thought I’d throw that idea out there too because I had the same thing happen after I installed some , I just removed a little bit of the coating off each side of one spring and everything was good after .

Is your 5 way switch grounded ?

 

[CadenGuitars]

I believe the cable is all the way in the problem has been replicated many times but I will definitely make sure of that.

Try moving in different positions around your room, face away from the amp, get as far away from the amps transformer as you can. If you notice the noise reduces, it's an emi issue.

Shielding the electronics cavity will help some (paint or copper tape. I like the XGP paint personally). Make sure there's some shielding (copper/foil tape) on the cavity cover too. Do NOT shield the pickup cavities. It absolutely draws in more noise. I have done extensive experiments on this bullshit and have reduced noise on multiple guitars by sanding off shielding paint that came in pickup cavities. Don't care if you run ground wires from the pickup cavity to the control cavity. Doesn't work. Shielding/conductive paint in pickup cavities is an incomplete faraday cage that simply draws in more interference that goes straight through the pickup. That's my story and I'm sticking to it.

Yeah I thought that would be the case if it was a shielding issue so I did move around the room with the guitar but there was no audible change when facing/standing in different directions. I have never shielded anything besides the control cavity so that's good to know I don't need to do the pickup cavities, saves me a bunch of work! As a side note, on these guitars the input jack has a separate small cavity, I assume I should probably do that too?

It’s hard to see but the solder joints from what I can tell look ok, so you have continuity from the jack housing (sleeve not tip) to the back of a pot housing? That would be the first thing I would check, since the jack sees the most punishment and that ground wire is usually the first to give up the ghost… but shielding the control cavity isn’t a bad Idea, it will also let you get in there and start looking you might find an issue you didn’t otherwise see with out moving wires and components, fraying wires cold solder joints ect…

Yeah it does have continuity from the jack sleeve to all the pots all the way up to the tuners. Yeah I think I may just have to shield it and hope that solves it. I can also try a new jack I may have one laying around.

Do you use those noiseless Floyd Rose springs ? It appears you are from what I can make out ? I ask because some of them are covered in polymer which is supposed to dampen spring noise but since the springs are covered all over with that stuff they prevent the bridge from grounding . Just an idea .. It could be the electronics but I just thought I’d throw that idea out there too because I had the same thing happen after I installed some , I just removed a little bit of the coating off each side of one spring and everything was good after .

Is your 5 way switch grounded ?

Funnily enough I just recently installed a tremel-no and noiseless springs but hadn't plugged the guitar in until a few days ago. I was getting these big popping noises and couldn't figure out why until I realised it was the springs. I have the normal springs in there now and the popping went but still getting the loud hum, I will try sand the springs where it makes contact with the claw and trem block so I can put them back in but for now it just has regular springs.

The 5 way switch is in fact not grounded, I did some googling on this and it seemed for the most part that most people said that they didn't need to be? Usually if I shield the cavity the 5 way switch is grounded by default as it will make contact with the shielding and thus the pots and everything else, but this guitar not having shielding means the switch is not grounded.

I did however hold a wire to the back of the volume pot and touched it to various places on the switch and it did not seem to effect the sound in anyway :/

Unless anyone has any other ideas about what the culprit could be I think I may just have to shield it and hope for the best. Thanks for the responses thus far.

 

[Mike]

You can shield the output jack cavity as well, however you need to be very careful to make sure that none of the lugs on the output jack are touching the shielding paint or tape. If they do, you risk causing a short and getting no sound.

An easier solution is to use something like a 1 conductor shielded wire to run to the output jack. Kind of kills two birds with one stone since it's shielding your output signal and also able to be used as your output jack hot & ground wires all in one.

 

[lost_horizon]

You could try adding another ground wire to the pot (similar to how the Ernie Ball Axis does it) by putting foil/copper tape on the back of the control cover and running another wire to there.

On the Axis it helped alot especially when I would take the cover off and accidentally forget to get that wire to touch the shielded cover.

 

[CadenGuitars]

You could try adding another ground wire to the pot (similar to how the Ernie Ball Axis does it) by putting foil/copper tape on the back of the control cover and running another wire to there.

On the Axis it helped alot especially when I would take the cover off and accidentally forget to get that wire to touch the shielded cover.

Okay great thanks for the suggestion, this will only take 1 minute so I will definitely try this when I get home and post the results.

 

[RandomPolishGuy]

Check your cable as well as your outlets. I had a grounding issue in my home so bad that if a cable touched the floor it's all you could hear and I think I tried everything on my guitar to fix it. I upgraded cables and got a Morley Hum Exterminator and it helped tremendously

 

[CadenGuitars]

Check your cable as well as your outlets. I had a grounding issue in my home so bad that if a cable touched the floor it's all you could hear and I think I tried everything on my guitar to fix it. I upgraded cables and got a Morley Hum Exterminator and it helped tremendously

I can do that, the only thing that makes me think that isn’t the issue is I own 8 or so electric guitars and 3 amps, all using the same outlet and I only get the issues with 1 guitar.

I also tried to shield the back of the cavity cover and grounded it to a pot - made no difference. I think I will just try shield the entire cavities and see what happens. Will be a little while as I am buying the paint from StewMac as the copper shielding tape would not suit the look of this guitar but once I purchase it and get around to doing it I will post results.

Cheers everyone

 

[RandomPolishGuy]

I can do that, the only thing that makes me think that isn’t the issue is I own 8 or so electric guitars and 3 amps, all using the same outlet and I only get the issues with 1 guitar.

I also tried to shield the back of the cavity cover and grounded it to a pot - made no difference. I think I will just try shield the entire cavities and see what happens. Will be a little while as I am buying the paint from StewMac as the copper shielding tape would not suit the look of this guitar but once I purchase it and get around to doing it I will post results.

Cheers everyone

That's definitely a mess. Get some shielding paint from GuitarFetish or your nearest retailer and it should clear it right up if all electronics are good. Same advice you've probably had a million times but hopefully it helps. I'm a luthier here in my small town so if you need any help feel free to dm. I have been doing this since I was 16

 

[RandomPolishGuy]

That's definitely a mess. Get some shielding paint from GuitarFetish or your nearest retailer and it should clear it right up if all electronics are good. Same advice you've probably had a million times but hopefully it helps. I'm a luthier here in my small town so if you need any help feel free to dm. I have been doing this since I was 16

I say shielding paint as you can paint the entire cavity with ease instead of cutting and sticking and folding the tape