Hum with both volumes not on full with NR Thunderbird solutions?

[bobyoung]

I also posted this in Bill's repair section but figured some of you Gibson experts here may have heard of this before and may have a solution.

Anyone here good with Thunderbird wiring? This is a year old NR T-Bird. I'm getting 60 cycle hum when I have both volumes below full with it in an amp I use at a weekly gig, it's not the amp as other basses don't do it there. I'm in Lima, Peru.

The power out here is 220 with one hot wire and a neutral, no grounds.

This one bass also will do it at home with Ampegs but reversing the plug solves the problem with them and none of my other basses hum here with both volumes below full on. I'm pretty sure it's something internal as diming both volumes increases any buzz pickup but eliminates the hum. No bass out of 6 I have here does this besides this T-Bird. The bass sounds great and both pickups sound normal. Any tips appreciated. This is with the same cord, I frequently play a Jazz at this club, also a Fender P/J with both volumes down too and no hum at all.
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[bobyoung]

I forgot to add, the hum diminishes considerably when I touch the strings.

[Ken]

Must be a grounding issue with the bass, no?

[bobyoung]

I don't know, I just checked all the wiring and the grounding is contiguous, I'm starting to think the pickups are picking up 60 cycle hum from the power.

[Ken]

Is the bridge grounded?

[bobyoung]

Yep, I went through it with a multimeter, everything that's supposed to be grounded is grounded, bridge, pickups, pots.

[Ken]

Sorry, that's all I've got.

[bobyoung]

Me too 

[Alanko]

I forgot to add, the hum diminishes considerably when I touch the strings.

If this is the case then there is no grounding issue with the bass. Not sure why folk jump on this solution at every turn.

Lack of ground at the outlet sounds sketchy, and presumably means your amp chassis isn't grounded?

[Basvarken]

You tell us the amp doesn't not have a grounded plug.
That's your culprit.
Any amp should be grounded as far as I'm concerned.

I think you'll be in danger of being electrocuted when your lips touch a microphone...

[bobyoung]

I'm in Lima, Peru and there are no grounds. It's single phase 220, neutral and a hot wire, I'm sure it's because of no grounds but no other bass I've got out here does it. I've gotten tingles from mics before but nothing serious. I don't know why they did it this way here but it's the whole city, other cities here have grounded systems. I'm going to shield it and see if that helps. Remember that most places in the U.S. had no grounds until the 70's. I am careful though with mics, you never know.

[bobyoung]

If this is the case then there is no grounding issue with the bass. Not sure why folk jump on this solution at every turn.

Lack of ground at the outlet sounds sketchy, and presumably means your amp chassis isn't grounded?

The whole city is like that, so was the U.S until about the mid 70's. There is no grounding issue with the bass. My point is that I've used a Fender Jazz, a Fender P/J, a Gibson EB4-L with no problems through this same amp, no hum, but the Thunderbird hums with both volumes below full which I find strange. I'm sure it is because of no ground but I'm going to shield it and see if that helps.

[Rob]

To me the less than full volume comment is the key somehow.
I would try jumpering out controls one at a time when you have it open for shielding.

[Basvarken]

To mr the less than fiukk volumr comment it the ket somehow.

[Rob]

LMAO!  Can't type on my tablet without glasses