Question about buzzing w/P90s and tube amp under certain circumstances

[bry4321]

I am more curious than anything. 

If have tone knob all the way to the right on my amp and guitar, and I am not touching the strings, AND and the front pickup is on and turned up, there is a light buzzing when I touch the metal by the pickup selector switch. If I turn the front pickup volume down using the guitar knob, or turn down the tone knob on guitar or amp, the buzzing goes away. 

Same thing with the rear pickup. Light buzzing with tone knobs all the way clockwise when rear pickup is selected with guitar volume cranked and I touch the metal ring under the pickup selector. It goes away if I turn the volume down on the rear pickup when it is selected.

No buzzing if I touch anywhere else but under the selector switch.

No buzzing if I touch the strings AND the metal by the selector. 

It looks like all the right wires are soldered to the selector switch but I need to take a closer look. 

I hope I have explained that clearly in case anyone has any thoughts. I have never had P-90 pickups before so maybe it is just a pickup thing. In case it's not obvious, I don't know anything about electronics. 

 

[butcher]

Pickup switch case needs to be grounded. 

[duncans]

P-90s are single coils. Single coils are noisy compared to humbucking pickups. Some will be noisier than others. But as Butcher stated it could be a grounding problem

[Jeff R]

FIRST ... don't discount environmental contributors to noise. Old houses with antiquated or poor grounding, florescent lighting, computer monitors, cell phones on top of amps or in pockets, neon wall signs, dimmer switches on walls, all can all create noise problems. If you haven't modified the guitar's cavity, or if you can't readily find the problem in visual inspection, test the guitar in other rooms, a friend's house, your local guitar shop, before you start disassembling the guitar.

There is always one direction you can face with single coils that will eliminate, or at least minimize, 60-cycle hum. Put your guitar on a strap, find that quiet direction in which to point yourself and the guitar as you check your work. You don't want to confuse normal P-90 60-cycle noise with wiring issue noise.

Also, no pedalboards, no effects, no wireless units, no using computers and/or plug-in software amp sims to diagnose and/or fix the issue. Use only the guitar, a good cable and a real guitar amp even if it's a small practice amp.

P-90s are typically two-conductor leads ... one connected to the coil start and another to the coil finish. Ground (coil start) goes to a pot back. Hot (coil finish) goes to a switch or a pot lug depending on the circuit. Because two-conductor pickups are simply a coil start and a coil finish, leads can be inverted and the pickup and the circuit still function. But that can create noise, especially if you touch pickup(s) poles. If your P-90s have metal braided shield leads, the braid itself is the ground (goes to pot back), the internal cloth-shielded wire is hot (goes to switch lug or pot lug. 

Make sure all pots, switch, jack, and lead from bridge are included the ground chain. Pot backsides should be connected in a simple A to B to C etc. series. Don't make a complete circle, or an enclosed triangle, or a starfish or random geometric art, or anything else overkill that might create a counterproductive loop in the circuit.

Switch, jack and the wire from the TOM/ST/bridge should be connected to the pot back circuit. I try to put them all on the same pot back to again eliminate any funky looping.

Make sure you have good solder joints. One cold solder joint to a pot back can maim what you're trying to do.

Pain in the butt, but sometimes the ground wire to the TOM or the ST comes loose internally ... and the bushing where it typically sits has to be pulled, the wire re-run and the bushing re-installed.

[HSB0531]

On 1/19/2023 at 5:58 PM, bry4321 said:

I am more curious than anything. 

If have tone knob all the way to the right on my amp and guitar, and I am not touching the strings, AND and the front pickup is on and turned up, there is a light buzzing when I touch the metal by the pickup selector switch. If I turn the front pickup volume down using the guitar knob, or turn down the tone knob on guitar or amp, the buzzing goes away. 

Same thing with the rear pickup. Light buzzing with tone knobs all the way clockwise when rear pickup is selected with guitar volume cranked and I touch the metal ring under the pickup selector. It goes away if I turn the volume down on the rear pickup when it is selected.

No buzzing if I touch anywhere else but under the selector switch.

No buzzing if I touch the strings AND the metal by the selector. 

It looks like all the right wires are soldered to the selector switch but I need to take a closer look. 

I hope I have explained that clearly in case anyone has any thoughts. I have never had P-90 pickups before so maybe it is just a pickup thing. In case it's not obvious, I don't know anything about electronics. 

 

If your fingers touch anything that's a ground, then the buzz should go away. And I would expect the toggle handle and mounting plate and nut to be grounded.  I would go to the website of whatever company made the pickups, and look at their wiring diagrams listed for the type pickup you have. Check it against the wiring on the guitar.  That should tell you if there's a miss-wiring in the guitar.

 

[Dave Scepter]

What I've done in the past "to aid in troubleshooting" is to get a jumper "alligator clip" ... attach one end to a good known ground, then touch other parts of the guitar to see if the hum goes away

[HSB0531]

On 1/20/2023 at 5:26 PM, Jeff R said:

FIRST ... don't discount environmental contributors to noise. Old houses with antiquated or poor grounding, florescent lighting, computer monitors, cell phones on top of amps or in pockets, neon wall signs, dimmer switches on walls, all can all create noise problems. If you haven't modified the guitar's cavity, or if you can't readily find the problem in visual inspection, test the guitar in other rooms, a friend's house, your local guitar shop, before you start disassembling the guitar.

There is always one direction you can face with single coils that will eliminate, or at least minimize, 60-cycle hum. Put your guitar on a strap, find that quiet direction in which to point yourself and the guitar as you check your work. You don't want to confuse normal P-90 60-cycle noise with wiring issue noise.

Also, no pedalboards, no effects, no wireless units, no using computers and/or plug-in software amp sims to diagnose and/or fix the issue. Use only the guitar, a good cable and a real guitar amp even if it's a small practice amp.

P-90s are typically two-conductor leads ... one connected to the coil start and another to the coil finish. Ground (coil start) goes to a pot back. Hot (coil finish) goes to a switch or a pot lug depending on the circuit. Because two-conductor pickups are simply a coil start and a coil finish, leads can be inverted and the pickup and the circuit still function. But that can create noise, especially if you touch pickup(s) poles. If your P-90s have metal braided shield leads, the braid itself is the ground (goes to pot back), the internal cloth-shielded wire is hot (goes to switch lug or pot lug. 

Make sure all pots, switch, jack, and lead from bridge are included the ground chain. Pot backsides should be connected in a simple A to B to C etc. series. Don't make a complete circle, or an enclosed triangle, or a starfish or random geometric art, or anything else overkill that might create a counterproductive loop in the circuit.

Switch, jack and the wire from the TOM/ST/bridge should be connected to the pot back circuit. I try to put them all on the same pot back to again eliminate any funky looping.

Make sure you have good solder joints. One cold solder joint to a pot back can maim what you're trying to do.

Pain in the butt, but sometimes the ground wire to the TOM or the ST comes loose internally ... and the bushing where it typically sits has to be pulled, the wire re-run and the bushing re-installed.

I'm glad you mentioned old houses and the wiring.

I had a Sears Silvertone guitar and Amp Case. I rebuilt the amp and still had slight hum/buzz problems.  I sold/delivered it locally and mentioned this, but when the buyer tried it out it was dead quiet.  The same thing happened with my Warm Audio WA73-EQ.  It has a buzz only when I use it at home.

 

[Hamer95USA]

   I like all of the responses to this thread and they're all useful & valid. I decided to uninstall the OEM Seymour Duncan Hot & Custom P-90 pickups and install a set of Mojotone Hot Quiet Coil P-90 pickups. For the amount of gain that I use onstage and not having to deal with noise issues, shielding, noise gate pedal, etc., the Hot Quiet Coil P-90 pickups work for that sound that I'm going for. 

  Here's an example of the '93 Special with the Mojotone Hot Quiet Coil P-90 and my Stiff 90-AD 50 watt amp head with Hot Mod EVO V2 installed:

https://www.youtube.com/watch?v=0OL87fSV0Y0&list=PLHiHk6kw0obhFzYZLrXy2wIzMTnoflS09

[Feynman]

Whoa - you guys sound great.  I looked at those pickups myself.  Glad to hear a positive review.

[JGravelin]

I've been helping customers with noisy single coil P90s for years and yes: copper shielding everywhere and top quality parts. The Mojotone QuietCoils are great and affordable, totally rip! The Fralin models (sidewinder style) are excellent as well but a different flavor. The Kinman offerings: Gold Standard. When I can beat those in sound and performance, it'll be a big day for sure and smiles all around.

On the cheap though, if you love the sound of your standard issue single coil P90s, copper shielding tape smartly applied with a separate ground wire is going to be your best friend. Use the contact-conductive stuff inside the cover, on top of the pickup bobbin, and around the coil itself making sure you've got a 100% contact  - solder a ground wire to this neatly applied shield - and solder directly to "black" ground at the output jack for best results.

You can do it!

[bry4321]

On 3/12/2023 at 10:30 PM, JGravelin said:

I've been helping customers with noisy single coil P90s for years and yes: copper shielding everywhere and top quality parts. The Mojotone QuietCoils are great and affordable, totally rip! The Fralin models (sidewinder style) are excellent as well but a different flavor. The Kinman offerings: Gold Standard. When I can beat those in sound and performance, it'll be a big day for sure and smiles all around.

On the cheap though, if you love the sound of your standard issue single coil P90s, copper shielding tape smartly applied with a separate ground wire is going to be your best friend. Use the contact-conductive stuff inside the cover, on top of the pickup bobbin, and around the coil itself making sure you've got a 100% contact  - solder a ground wire to this neatly applied shield - and solder directly to "black" ground at the output jack for best results.

You can do it!

Thank you, somehow I missed this. Thanks to @FeynmanI have 2 Fralin P90 pickups and no noise. At least, not the buzzing I mentioned in the original post. Vanguard had been equipped with (I assume original) Duncan pickups labeled 2N/3B.  I have no idea if the pickups were the problem, or grounding/wiring etc. Probably the latter. Sorry I didn't see your message @JGravelinto give that a try and I appreciate all the suggestions.