Guitar Humming & Feedback...

[dodgefdl]

I have a les paul knock-off that seems to have an electrical problem. It sounds great, but as soon as I stop playing, I get unstoppable squealing. I'm playing it through my Marshall VS100, just like all my other guitars, but this one squeals like a pig! Unless I turn the volume all the way down, I get squealing. If I'm on my clean channel, I can mute the strings with my right hand over the pickups, and it stops the humming. As soon as I take my hand off the strings, it starts humming again...is there a ground problem somewhere or is the switch not well isolated? How can I fix this? I wouldn't mind keeping these pickups, but I can't deal with all the squealing...what do I do?

[Regis]

Sounds like microphonic pickups and a bad ground of some kind. I take it you are playing with a lot of volume and gain. If the pickups are not potted and/or cheaply made then chances are that's the issue.

The humming is a wiring problem, either a defect or something has come loose in the wiring. I suppose you could have a bad pickup too, but unlikely.

I don't use a high gain amp but I do play loud with lots of overdrive and have had pickups that squeal. Potting solved it mostly.

There are lots of wiring diagrams around the net, as well as instructions on how to pot pickups, do some googling.

[dodgefdl]

Thanks for your advice...much appreciated. I've heard of the term microphonic before and have done a little reading on it...I just have to find time to do some more. The term potting seems to be used rather loosely though...is it basically dipping the coils in wax, then putting it all back together? I am going to take it apart and take a close look at it to see if I can find a bad ground...but do you think the switch could just be the problem? I'd hate to muck with the pickups if the switch is the problem...

[Regis]

Here is a good page on potting pickups. I've done it, it's no big deal.

Here is a page on wiring schematics for guitar.

There should be a wire connecting the bridge to the ground on the guitar. That is probably why you are getting hum when you let go of the guitar.

I doubt if it's the switch.

[Paleo Pete]

I'll second the pickup potting advice, not difficult and makes a big difference. I've done several. A couple of things to note...

Get out your digital camera and take a few pictures of the wiring before you desolder the pickup. You'll thank me later...

Handle gently, the wires are thin. Use needle nose pliers or hemostats to handle while dipping, the wax is hot. Try to hold it by the bottom metal plate, not the wires, and keep the wires out of the wax. Don't touch the windings. If they have tape covering them, leave it on. The wax will still soak in.

Watch the temperature closely. I use an electric potpourri pot, works nicely and small enough it doesn't take much storage space. I scrounged up a lid that fits from a resale shop for a buck, that keeps dust out while stored. (I do guitar repairs for other people too so I need to have it available for future use, many players will only need it once, storeage may not be an issue.)

Don't be impatient, it will take around 15-20 minutes for the wax to soak in and all the bubbles to stop. Clean the wax off the top while still hot, it's a lot easier to get it all off.

I think Regis is dead on about the hum too, ground wire is always my number one thing to check/install.

[Regis]

Pete is correct about taking pictures, doing that has saved my bacon more than once, and cooked it when I didn't. (Oh, I'll remember which wire goes where....Right!!)

Sometimes I draw a diagram or schematic of what I'm dismantling with color code notations, terminal designations, which wire goes where, etc.

[dodgefdl]

Thanks a lot guys! I haven't had time to work on it yet...hopefully I'll get the chance soon...like this year...lol. I'm also have a broken amp though too...my old man knocked over my Marshall halfstack and the head is dead...I almost cried. Good thing I have other amps and guitars to play with. I will likely work on the amp first, then try to fix that guitar. I really appreciate the advice. I will likely attempt the potting exercise even though I've never done it. What kind of wax would I use...just parrafin? Would I submerge the entire pickup...without the gold covers of course...I will have to do some more reading before I jump into it head first. I want to know exactly what to do before I mess with anything. First things first though...I will check that ground. Thanks again.

[Regis]

Thanks a lot guys! I haven't had time to work on it yet...hopefully I'll get the chance soon...like this year...lol. I'm also have a broken amp though too...my old man knocked over my Marshall halfstack and the head is dead...I almost cried. Good thing I have other amps and guitars to play with. I will likely work on the amp first, then try to fix that guitar. I really appreciate the advice. I will likely attempt the potting exercise even though I've never done it. What kind of wax would I use...just parrafin? Would I submerge the entire pickup...without the gold covers of course...I will have to do some more reading before I jump into it head first. I want to know exactly what to do before I mess with anything. First things first though...I will check that ground. Thanks again.

Check the link above for details about potting. Use beeswax from a hobby shop or a Michaels. Leave the covers on and clean after potting.