Serious grounding problem with Quarter Pounders

[thornev]

Hi All, I'm a new member. I've used SD pickups in several of my guitars, but this installation has me pulling my hair out. The details...

I bought the Quarter Pounder kit with both Telecaster neck and bridge pickups. Each pickup has 2 leads and the neck pickup has that jumper for the neck pickup's chrome plated cover. I installed and wired the pickups with a 4-way switch, the switch and wiring instructions at this web page:
https://www.seymourduncan.com/blog/...-cool-alternate-wiring-schemes-for-telecaster

I did clip the jumper and added a new lead to the pickup's cover, grounded to the back of the volume pot. I hooked up the connections using alligator clips so I can test that I wired correctly before committing the wiring. All 4 switch settings seem to work correctly except I get a very loud grounding hum in all 4 switch positions. It's louder when the bridge pickup is active. I've checked all my ground connections and they seem correct including the wire under the bridge plate which connects to the back of the volume pot. I triple and quadruple checked all my wiring and I believe I have it correctly.

This guitar is an Ibanez 1977 Silver Series Tele signed by Keith Richards and given to me by my mom for my 40th birthday. It's legit as it was purchased from Southeby's auction house. I love playing it and the original pickups were hot but uneven as far as the output from each string. That's why I wanted the SD pickups - to improve the evenness of the string response.

Can someone please provide some ideas as to what I can examine to get rid of the hum? I should also explain that the switch plate is from a prewired kit from 920D Custom, the T4W-C. The 4-way Oak Grigsby switch is the same as the SD 4-way wiring referred to above so I assumed it would work just fine. However, there is one difference - the capacitor is not on the tone pot. It is where most guitar caps go, between the volume and tone pots. With my knowledge of electrical wiring, I don't believe this difference would cause the grounding hum.

Thanks for listening and hopefully, replying. Rock on my fellow musical compatriots !! Thorne

UPDATE: I'm getting a Super Switch today so if your suggestions would be better suited using that blade switch, I'm all up for any and all ideas. I would prefer a 5-way set of pickup combos as long as they include the standard Tele 3-way, both pups in series and both to provide that Strat clucking sound. I have hardly any understanding of how to wire these blade switches so please be as detailed as reasonable with your wiring sugs. Thank you.

UPDATE 2: I just studied guitar wiring here:
https://www.fralinpickups.com/2017/06/18/blade-switch-basics/
I could never understand how jumpering A0 to B0 works, but now I think I understand.

 

[jeremy]

theres no reason there should be lots of hum, just normal single coil hum. i do find that things are noisier when using alligator clips than when things are soldered. you do have a ground wire to the bridge, yes? the cap being between the volume and tone, vs tone and ground isnt an issue

 

[thornev]

Hi Jeremy. Yes, there is a bare wire under the bridge plate wired to the back of the volume pot. That was my first suspect since the bridge pup hum is louder. You're suggesting that the origin of the hum is external via the alligator clips. I tried moving the guitar around and a nearby transistor radio was producing some RFI/EFI, but not enough to be the root cause of the noise.

 

[thornev]

Aha... I moved the guitar to be on my lap, away from anything that could cause noise. There still is hum, but it completely goes away when I touch anything on the guitar that is grounded to the back of the volume or tone pots. That has to be a clue as to what is causing the hum, right? I neglected to mention that I'm doing all this with the strings removed. I assume that has no effect on the noise except that touching the strings will also remove thew hum because they are also grounded.

I'll start researching online, but I'd appreciate any ideas of what else needs to be grounded to eradicate the hum. Surely this grounding hum is a common problem with definitive solutions. Thorne

PS - I've been trying to add a picture of me as an avatar, but every time I try to upload it, I get an error. No explanation as to why, just "error" when uploading. Anyone know how to solve that one? I use the Chrome browser on Windows 11 Pro x64.

 

[jeremy]

there is a glitch in the forum that causes the avatar issue. mincer or myself may be able to add the pic to your profile

as far as the hum, if it goes away when you touch anything metal, its a grounding issue. do you have a meter? if i were you, id wire everything up. if it still hums, then check grounding continuity on all components

 

[thornev]

I have several meters so I will proceed to test continuity of all components and see which one(s) may be shorted.

jeremy, When you say "wire everything up," do you mean solder, not alligator clips? Right now I have a 4-way switch, but today I received my 5-way super switch which will be the permanent switch. I want to test it first to ensure I've wired correctly (hum or no hum) as far as functionality of each switch position and then I'll solder. It will be a marvel if soldering eradicates the hum.

 

[thornev]

I put my meter on continuity, negative lead on guitar ground (the bridge plate), and touched the positive lead to everything. I got no unexpected shorts except one case about which I'm unsure... When I touch the positive lead to the bridge pickup "-", I get continuity which is expected because in the wiring diagram (see above post) that pickup lead is connected to the back of the tone pot. But when I touch the positive lead to the "-" of the neck pickup, I get no continuity. In the wiring diagram, that lead is connected to a 4-way switch lug which, as far as I can tell, is NOT connected to ground. But I'm unsure if it SHOULD be connected to ground since it's the negative lead of the pickup. I trust the wiring diagram, but I've been bitten before by trusting.

 

[thornev]

Additionally, I've discovered that the hum is present only when the switch is in positions 1 and 4. That has to be a big clue, but I don't know what it means right now. Position 1 is bridge only. Position 4 is bridge and neck in series. Positions 2 (bridge and neck parallel) and 3 (neck only) are quiet.

UPDATE: This can't be a shielding issue, can it? I had no hum issue with the 4-way and original stock pickups so I wouldn't expect shielding suddenly to become a solution.

 

[jeremy]

it should not be a shielding issue if it wasnt before. and yes, i mean wire it all up properly. as far as why the bridge alone and series hum, but the others dont, including parallel, i dont know. though it would suggest something isnt grounded properly on the bridge pup. when in parallel, the neck pup ground will work for both pups. when in series, that isnt the case

 

[thornev]

I installed the 5-way Super Switch, wired up with alligator clips just to test functional correctness, and I'm sad to report the loud hum is still present in switch positions 2 (neck & bridge in series, out of phase), and 4 (bridge & neck series, in phase). I get a mild shock and a loud pop noise when I touch the guitar ground after testing switch positions, or not having touched the guitar for a few minutes. Static electricity buildup I suppose. Always happens during Winter.

So, maybe it is the clips that causes shoddy connections, only one way to find out. Otherwise, I've examined both pickups and I don't see anything out of the ordinary. If I can't fix this noise, I have no ideas for other options. I can't go back to the stock pups because of the uneven string response. Research continues... Thorne

UPDATE: Another observation - the noise gets louder as I turn up the volume. Turning the tone pot also affects the noise as you would expect with a tone pot.

UPDATE 2: I hooked up my guitar to a battery-powered amp to remove the 60Hz noise as a variable. In this case I get MORE noise when I touch a guitar ground when the switch is on positions 2 and 4 ! Positions 1, 3 and 5 are quiet.

 

[thornev]

when in parallel, the neck pup ground will work for both pups. when in series, that isnt the case

jeremy - Can you please elaborate on this statement? What is it about the neck pup ground that makes it work for the bridge pup too and why doesn't it work when the pups are in series? Maybe there's a clue there I can use. Thanks for your responses. Thorne

 

[thornev]

I found that the bridge plate bare wire that is a ground (one of 2 grounds as the negative lead of the bridge pup is connected to the back of the volume pup) for the bridge pickup is NOT electrically-connected to the neck pup negative lead which is connected to one of the common lugs on the 5-way Super Switch. Is that normal? I would have thought that the grounding leads for both pickups would be connected somehow.

 

[jeremy]

it depends on the wiring as far as the 5way

in parallel, both hot wires and both ground wires go to their respective places. in series, one pup feeds into the other so there is only one hot and one ground connection

 

[thornev]

jeremy - Here's the wiring of the 5-way super switch. Does this help at all?

 

[thornev]

I'm going to solder the leads after cutting them to be as short as possible. Hopefully soldering will eliminate the noise. If not, the only other option I can see is restore the stock pickups. I have to believe there is a solution though. I wish I were more savvy about guitar electronics.

 

[thornev]

Here is the wiring diagram of the Tele pre-wired plate to which I've connected the 5-way Super Switch. That pre-wired plate came with a 4-way switch as pictured. Can anyone see a reason that this grounding issue I have is because I'm replacing the 4-way with a 5-way? Or perhaps should the 5-way be wired differently than what I posted in a previous post above in post 14?

 

[eclecticsynergy]

Aside from the wiring issue, bear in mind that QPs are inherently quite noisy.
Natural consequence of massive winding in a pickup with zero hum rejection.
I love 'em. But quiet they're not.

 

[thornev]

eclecticsynergy - Love your signature about voodoo. I get about QP's being noisy, but THIS much noise can't be normal. I don't know if I can post a sound bite, but aside from what you say, the loudest noise occurs on only 2 positions. I still gotta believe it's fixable, but I'm starting to run out of ideas.

 

[thornev]

Well...I wired up the Quarter Pounders to the 5-way Super Switch and... ground noise is GONE !!!! (well, unless I crank up the pedalboard volume with all sorts of distortion). You were right, @jeremy, that those alligator clips and long wires acted as antennae for every little RFI/EFI in the room. I'm a happy guitarist. Now to string it up and see how those pups respond. Yahoo !!

Thank you @jeremy and @eclecticsynergy for your feedback. Hopefully I'll be helpful to others in the future. Thorne