Almost there: Now my humbuckers hum like a single coil with the overdrive pedal on. Add a ground to body?

[Stewart1983]

Okay, again, thanks for assisting me with my previous grounding issue of the braided shield making contact with either the copper shield pickguard or tab at the blade switch.

So everything is working correctly, except, when I did the tap test before stringing up, there is an overall hum. A dull hum, like I have an overdrive pedal turned on in a single coil guitar. Volume off makes it go away (duh) and messing with the tone controls naturally dulls and brightens this hum.

The braided shield was stripped back to the grounded pot, so nothing to affect pickup wires interferring. I switched from the original Alpha pots to CTS 500k. All components are new (CRL blade switch, switchcraft output jack.)

I’ve added a wire from the grounded pot attached to a screw, screwed into the body control cavity before. I’m always mindful of good solder technique to avoid the whole cold solder rabbit hole scavenger hunt.

I didn’t take a pic of the circuit with the output jack and claw ground wires. I swear I connected the tip and sleeve wires correctly. But I’ve had similar results when those wires were reversed. God I hope it’s not that (yet still that would be a simple solution.)

No shielding in the control cavity. Didn’t think I needed it with humbuckers.

Again, lots going on in my life, working on this guitar was supposed to be a life distraction, but somehow my focus is off for troubleshooting. You’d think after 25 years of wiring circuits I’d have this down in my sleep by now.

 

[Verne Bunsen]

The guitar volume eliminating the hum is not necessarily a “duh”, as a hum could potentially originate elsewhere in the signal chain. So that is a valuable data point. Did the tap test produce the expected results (pickups active as expected for each switch position)? Is the hum present in all switch positions? Does the hum change/stop when you touch the strings or other grounded metal component on the guitar?

 

[rauchman]

Not sure if the body used is a Strat body, but did you connect the ground to the trem claw?
If using something like a TOM bridge, did you connect the ground to the bridge post?
If using a Tele bridge or Flat Mount Tele/Strat bridge, did you connect to the underside of the bridge?

 

[Stewart1983]

The guitar volume eliminating the hum is not necessarily a “duh”, as a hum could potentially originate elsewhere in the signal chain. So that is a valuable data point. Did the tap test produce the expected results (pickups active as expected for each switch position)? Is the hum present in all switch positions? Does the hum change/stop when you touch the strings or other grounded metal component on the guitar?

 

[Stewart1983]

Test showed all appropriate pickup positions. Hum was present in all three positions. No disappearance of hum when touching any metal parts.

 

[Stewart1983]

Not sure if the body used is a Strat body, but did you connect the ground to the trem claw?
If using something like a TOM bridge, did you connect the ground to the bridge post?
If using a Tele bridge or Flat Mount Tele/Strat bridge, did you connect to the underside of the bridge?

Yes, ground from claw to volume pot.

 

[Verne Bunsen]

The next thing I would do is use a multimeter to verify continuity from the jack sleeve to each item that should be seeing ground: pot cases, grounded volume pot lug, the shielding foil, the trem claw, the bridge itself (which should be seeing ground through the claw), the switch frame, the pickup frames, the braid on the leads, and whatever I may be missing. It should all ring out with the jack sleeve. If not, investigate. If everything checks out there I would be starting to suspect a cooked pot. I’d disconnect the switch output and the jack tip from the rest of the circuit and go directly from the switch to the jack and see if the hum is present.

 

[rauchman]

I'm probably wrong, but the black wire coming off of the 3 way switch, looks to be used as a ground. Is that correct?

For myself, I don't recall a ground coming off of a switch.

 

[Verne Bunsen]

I'm probably wrong, but the black wire coming off of the 3 way switch, looks to be used as a ground. Is that correct?

For myself, I don't recall a ground coming off of a switch.

edit: I think that is the conductor wire coming out of the braid, rather than a wire going to ground

 

[Stewart1983]

I'm probably wrong, but the black wire coming off of the 3 way switch, looks to be used as a ground. Is that correct?

For myself, I don't recall a ground coming off of a switch.

That’s the bridge pickup hot wire.

 

[Spud]

All good advice above. The bare wire being used to bridge the switch, could that be contacting unintended parts of the switch (or its solder)

 

[Spud]

Hey Stewart!

 

[Stewart1983]

All good advice above. The bare wire being used to bridge the switch, could that be contacting unintended parts of the switch (or its solder)

No. Although the wire is cloth, it’s pretty ridged and stays in place. I wouldn’t think the insulated claw, sleeve & tip would cause problems with contact. But I could be wrong.

 

[Spud]

Re check jack

 

[rockandroller]

You did not mention if you were touching the BRIDGE when you did your (unstrung) check?

Generally, 'string ground noise reduction' (reduction of EFI, Electrostatic noise, and EMI resonance 'buzz') doesnt work very well if you are not touching the strings (it is your body that acts as the big biological antenna, inducing that sort of noise into the nearby pickups, so you need to ground yourself...).

You could test that by seeing if noise is reduced when you contact the bridge ( the bridge is grounded, right?) or even just the grounded shield of the plug.
Is your AMP properly grounded??
Have you checked the outlet with an outlet tester?

The foil shielding does nothing to prevent actual '60-cycle-hum'... and that kind of magnetic field induced by AC can vary depending on the equipment and environment.
Do other 'known good' guitars behave the same way when plugged in to the same cable/amp?
Does the noise reduce if you ROTATE the guitar body in different directions?
(this indicates you are dealing with strong local energy fields, and that should effect all guitars about the same, if they have comparable pickups)

 

[rauchman]

That’s the bridge pickup hot wire.

I was referring to the black wires. They look to be soldered to the back side of the 3 way, and it's routed as a ground to the top of the Vol pot. I'm very far from a wiring expert, but haven't seen that done.