Please help with guitar grounding issue

ftumch · January 2020

Hi all, hoping to appeal to your generous nature I really need some help.
Having experienced my woeful pickup fitting skills before I bought a pre wired 50's les paul harness from Alegree of this parish.
Removed old emg's and pots.
Fit new harness, wire up pickups and switch and I have a grounding issue. Major hum on both pickups that goes away when I touch any of the hardware.

This is the harness.

http://i1131.photobucket.com/albums/m544/kevinstead/Mobile Uploads/Screenshot_20200103-184034_Samsung Internet.jpg

I wired
Neck pickup to lug 1 of neck volume pot
Grounded braided wire to back of same pot
Bridge ground to back of same pot
Neck switch to middle lug of same pot

Bridge pickup to lug 1 of bridge pot
Bridge switch to middle lug of same pot
Switch ground to back of same pot

Switch hot to tip of input
Sleeve of input to back of bridge tone pot.

Any help is very much appreciated. I'm sure the harness isn't the issue, it's either I've soldered wrong or I've soldered poorly. Both are more than possible.

Thanks

ICBM · January 2020

Unfortunately I can't see your pic because you've used Photobucket.

Do you have the strings on yet? If not you'll get a much worse buzz when you're not touching the hardware. Some buzz when not touching the strings or other grounded hardware is normal with passive pickups, and if it goes away when you're touching the strings (or tailpiece if the strings aren't on yet) then it is grounded correctly.

ftumch · January 2020

Lp wiring https://imgur.com/gallery/AqqHd01

ftumch · January 2020

@ICBM thanks for looking, I've uploaded to imgur so hopefully you can see it now? I've put it all back together, strings on. The hum is definitely more than the usual noise.

Roland · January 2020

ftumch · January 2020

Thanks @Roland your a gent.

ICBM · January 2020

Is the shield connected to ground on the cable between the switch and the jack? If not you have over a foot of unshielded wire there, which will certainly buzz.

I’m assuming this is buzz and not hum, by the way, since it goes away when you touch the hardware.

You also have a ground loop around the pots, which is not ideal, but that will cause a slight hum which is not affected by touching anything.

ftumch · January 2020

Sorry for being dense, when you say shield on the switch to jack cable what do you mean? It's not a braided wire, is that what you mean? The switch is grounded to the back of the bridge vol pot and the switch is grounded to the back of the bridge tone pot, no other ground between the two. How do I fix this?
Yeah its buzz not hum, my fault sorry.
How do I remove the ground loop?
Really appreciate your help.

ICBM · January 2020

The cable that goes up to the switch should have a foil lining and a bare wire that’s in contact with it. The bare wire needs to be soldered to a volume pot, even if there is another core wire being used to connect the ground. Ideally the cable from the jack to where it’s connected to this cable should be shielded too.

The ground loop on the pots is because the braided cables from the pickups are touching each other. You either need to put sleeving on these so they’re not, or remove one of the links between the pot casings.

My preferred way of doing it is to make the neck volume the ‘master’ ground, the neck tone and bridge volume connected to it (which means you don’t need to worry about the braided cables), and the bridge tone to the bridge volume.

ftumch · January 2020

That's odd, I've used the same switch and switch cable that was in there previously with the emg's 81 and 85 and it was dead silent. Is that because they were active?
Do you think I need to replace whole switch wire part for one with a shield?

ICBM · January 2020

ftumch said:

That's odd, I've used the same switch and switch cable that was in there previously with the emg's 81 and 85 and it was dead silent. Is that because they were active?
Do you think I need to replace whole switch wire part for one with a shield?

The EMGs won't pick up the same amount of noise at all, they're active and low impedance, which suppresses noise very effectively. (Which is why all professional mics are low impedance.)

Personally, I prefer to use three pieces of standard braided cable, one directly from the jack to the switch and two from the switch back to the volume pots, exactly as Gibson did it traditionally. The only thing you need to watch out for is the bare braiding shorting against any of the terminals on the switch or the controls, you either need to make sure it stays out of the way or put some sleeving on it.

Funkfingers · January 2020

EMG installation instructions usually recommend detaching the bridge ground wire at the controls end. If this had been done, the wire may require reattaching to a pot chassis or ground post on the PCB.

ftumch · January 2020

Funkfingers said:

EMG installation instructions usually recommend detaching the bridge ground wire at the controls end. If this had been done, the wire may require reattaching to a pot chassis or ground post on the PCB.

I re soldered the bridge ground to the back of the porch, I dont know if it's still connected the other end though I see no reason why not. Thanks though.

ftumch · January 2020

ICBM said:

ftumch said:

That's odd, I've used the same switch and switch cable that was in there previously with the emg's 81 and 85 and it was dead silent. Is that because they were active?
Do you think I need to replace whole switch wire part for one with a shield?

The EMGs won't pick up the same amount of noise at all, they're active and low impedance, which suppresses noise very effectively. (Which is why all professional mics are low impedance.)

Personally, I prefer to use three pieces of standard braided cable, one directly from the jack to the switch and two from the switch back to the volume pots, exactly as Gibson did it traditionally. The only thing you need to watch out for is the bare braiding shorting against any of the terminals on the switch or the controls, you either need to make sure it stays out of the way or put some sleeving on it.

I think I'll get some new shielded cable and some sleeving and just completely redo the switch and input wiring then. Thanks ICBM.

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Please help with guitar grounding issue

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