How to systematically remove hum?

[thor666]

Hmm in short I have 2 stacked humbuckers and a JB Jr on my guitar, and the guitar is still humming at 1,3,5, unless i put my hand on the bridge (or anywhere metal, strings etc).

Not intending to open the guitar up and resolder again for now, as i'm waiting for a midboost to come inside the guitar first

my question is, is there any systematic way to check which part is incorrectly/unproperly grounded? it seems a lot to find out from the whole wiring (and especially if i'm going to complicate it by dropping a midboost and maybe piezos as well...)

TIA! :beerchug:

 

[Robert S.]

Re: How to systematically remove hum?

Hey thor, here's the deal. A bad ground can be caused by a number of things. It sounds like you have a Strat type guitar so lets start there. It's important that if your guitar has a pickguard that is it sheilded. If the guard does not have a sheet of foil on the guard then you need to put one on. Tin foil and adhesive spray is the easiest method. The foil will not only give you a ground path to all the pots but to the pickup mounts and switch as well. This will help cure hum and will cure static type "popping" when you touch the screws on the guitar.

The next thing to look at is your bridge ground. Using an ohm meter, check for continuity between the bridge and the sleeve of the output jack. If that reading is not zero ohms, you need to run a wire from the bridge to the guitars guts. The best place to locate that wire is wherever you have the output jacks sleeve wire attached.

Most times if those two thing are correct and you still have hum then you have a faulty pot. Some pots have internal problems that cause hum and while the pot may meter out correctly it still creates noise. The way to find the offending component is a hassle but it is do-able.

Disconnect the output jack wires from the volume pot and grounding point. Wire the bridge ground and the pickups ground directly to the jacks sleeve lead. Wire the bridge hot to the tip lead of the output jack. This isolates the guitars components from the circuit. Most times doing this makes the hum disappear. If it doesn't, then replace the jack and test again.

Once you have the guitar hum free with the bridge humbucker and bridge wired directly to the guitar you can proceed. Add the switch to the circuit by wiring pickup - switch - jack. If the hum returns then you either have to ground the switch chassis or replace it. You can check the ground with an ohm meter from the switch chassis to the jack sleeve.

Then add the volume pot to the circuit, pickup - switch - pot -jack. Keep adding one component at a time until you rule out each component as the problem.

This is a commonly asked question and I have answered it a few times receintly. I should have this one added to the FAQs section.

It's a bit of work but it will isolate and cure your problem. It is also possible that you are suffereing from a bad ground from your electrical source and that is adding a grund type of noise to your rig. Use a different guitar on your gear and make sure the problem isn't with your source juice. I am in an older house with electrical "issues" and my HBs can hum a bit depending on how I stand. It's even worse when Im using "stacks" for some reason, probably the coil locations and lesser mids/noise cancellation.

 

[thor666]

Re: How to systematically remove hum?

thanks Robert...

yea this should be a sticky in the Vault (if it isn't yet...).. or on the SD FAQs... would help newbie guitarists a lot. :burnout:

 

[Gary Ladd]

Re: How to systematically remove hum?

Well, you got the number one rule down in "How to systematically remove hum", using all the same brand PuPs per guitar...

Mixing & matching PuPs is a crap shoot at best in my experience... :smack:

 

[thor666]

Re: How to systematically remove hum?

all of them are Seymour Duncans... SD Classic Stack neck, bridge and a JB-Jr. I've been much more lucky with SDs than Dimarzios so far (although I really should give the Virtual Vintage series a try someday.)

agree with you... the wiring colors can be a hell of a pain to figure...

 

[Gary Ladd]

Re: How to systematically remove hum?

all of them are Seymour Duncans... SD Classic Stack neck, bridge and a JB-Jr. I've been much more lucky with SDs than Dimarzios so far (although I really should give the Virtual Vintage series a try someday.)

agree with you... the wiring colors can be a hell of a pain to figure...

It's the lack of info on coil wind/polarity that I find exceptionally lame...and the moronic solution some "experts" give for solving the problem of phase mis-match by switching the ground/hot leads.

:smack: