another grounding issue...

[L-1329]

I really could use some input here. I have a Warmoth bass at a builder's, and when first played has a bad grounding problem. What I could use is some basic info on grounding so I understand what he's telling me better. The bass has an OBP3 pre, Nord Dual Coil pups each with a three way switch for parallel, coil tap, and series. The control cavity and pickup cavities are shielded, and he checked all the continuity of the ground wiring. Says it's all good. Obviously something in there isn't hooked up right. Would any of you be able to tell, in words a newb can follow, how things need to be wired to get the bass silent? Any help is certainly appreciated...

 

[luknfur]

I really could use some input here. I have a Warmoth bass at a builder's, and when first played has a bad grounding problem. What I could use is some basic info on grounding so I understand what he's telling me better. The bass has an OBP3 pre, Nord Dual Coil pups each with a three way switch for parallel, coil tap, and series. The control cavity and pickup cavities are shielded, and he checked all the continuity of the ground wiring. Says it's all good. Obviously something in there isn't hooked up right. Would any of you be able to tell, in words a newb can follow, how things need to be wired to get the bass silent? Any help is certainly appreciated...

FWIW:

there's lots of information available from a search regarding grounding issues. As simple as it is it can take a while to soak in. You've got a guy I assume you're paying to do the work so knows the situation and what your options are so there's you're ticket - unless he doesn't know what the problem is. Cramming a bunch of junk in a tight space can be a nightmare.

A few things stand out to me:

there's nothing better for shorts than a shielded cavity - especially if it's crammed with stuff. I put electrical tape below all pot lugs and between any hot lugs and bay way. In my experience, a meter is only an indication and not definitive. Did he check jack to bridge for ground? Maybe the bridge wire's lost contact with the bridge.

Mini-switches are ideal for faulty connections

By coil tap I assume you mean "single" coil operation which is not the same thing. A typical humbucker will hum in single coil operation becuase it's not longer humbucking - unless it's tied in with the single coil of another pup.

But it's interesting you should mention a Warmoth cause I just had a guy email today about a set of SD classic stacks he bought over 7 months ago that he's having a similar problem with - in a Warmoth. But I'd speculate there's a closer chance of the source be the same luthier/tech than same bass. To my knowledge, there's no such thing as a defective bass when it comes to grounding.

 

[L-1329]

Thanks for the reply. I am going through as many threads as I can on this to educate myself. This builder either doesn't know, or doesn't want to take the time to figure out the problem, and I don't think I am going to keep the bass there if that's the case. At least the assembly work was very good. It is not single coil hum, but definetly a bad ground.

I hadn't thought about shorts from the shielding, and the pots. When he mounted the pots in, the top was so thick he couldn't use the washers on the top side, so maybe that is a possible source inside. There may not be enough left to put some electrical tape between them. And do the mini toggles need grounded as well? If so I don't know if they are but that would be an easy solution. When I get this bass home I will be able to open it up and see what's what. Then I am sure I will be looking for more advice!

 

[luknfur]

QUOTE]

FWIW:

If he could barely get a washer on it that's an indication their's a possibility the pot lugs got sucked into contact with the shielding. If you take a meter and go from each lug to the shield that may tell you. If space is tight and you're not getting good connection with the meter leads, the meter reading won't be accurate. I can understand him not wanting to take the time but you paid him to produce a product that worked properly and that's not happening it sounds like. That can be a real nightmare if you go tearing into it so be prepared to deal with it. You may not have a working bass for a while.

You might even consder taking it to another luthier before tearing into it - at least to get his take and price. Also mentioning as much may be just the ticket to motivate this guy to straighten it out. About the only thing a lutheir likes less than stupid customers is another local luthier cleaning up his mess.

Luthiers can be strange people and you have to use your own judgement about how far you can push them. For future work, I would never go back to someone I couldn't work with. I would definitely ask him if he checked ground from bridge to jack. There's a possibility he pulled the bridge ground away from contact with the bridge in wiring the harness up. That's an easy quick check and any stooge can do it. I would also check that myself no matter what he says. You could end up tearing the control bay all apart when the problem was never even there to begin with.

Toggles usually don't need grounding but I have seen it done but I don't know why it was done it that particular case.