Help with graphite acoustic hum. (A bit of an emergency.)

[Artie]

Hey all. I've got a problem here. It's a customers Martin Graphite X Dreadnought acoustic-electric. 60-cycle hum is much louder than the guitar signal. I can take an alligator clip and connect it to a string, and then touch the output jack ground, and the hum goes dead silent. I'm using an inspection mirror to look inside and there's no broken wires. No bad grounds. The output jack mounts to a wooden block. The preamp mounts to the graphite sides, but through a plastic insulating system. Its like they didn't want it to be grounded.

Surely this guitar couldn't have come from the factory with this condition. (Could it?)

I'm looking at the Mitchels PlateMate, which would work, but it's got mixed reviews for changing the sound of the guitar. (Not good.)

Any of you luthiers out there have any ideas? I've got to get this done tonight. :sad:

Help, my friends.

Artie

P.S. I consider myself a fairly competent tech, who's dealt with ground problems many times in the past. But this is my first graphite acoustic.

 

[Artie]

Re: Help with graphite acoustic hum. (A bit of an emergency.)

I think we got it. The only "ground" between the strings and body, and the output jack, was a tiny bit of copper at the end of the transducer, under the bridge. Pathetic. You'ld think Martin could do better. But that's ok. This is one for the "books". I won't be fooled again.

Artie

 

[J E C]

Re: Help with graphite acoustic hum. (A bit of an emergency.)

Good to hear you got it. The only thing I could think of with out seeing it (in my hand that is) is the possibility of a connection or a part of a board touching the guitar were there is no finish. This could possibly ground or short some thing out due to the fact that graphite fiber is conductive.

 

[Bludave]

Re: Help with graphite acoustic hum. (A bit of an emergency.)

I was going to say that sounds like a grounding problem...

 

[Rand-O-Monium]

Re: Help with graphite acoustic hum. (A bit of an emergency.)

Glad ya got it ironed out!!!

 

[Artie]

Re: Help with graphite acoustic hum. (A bit of an emergency.)

Dang. We don't have it ironed out. The problem I mentioned is the problem, (the ground between the under-saddle transducers shield and the body), but resolving it is turning out to be harder than meets the eye. I hate dealing with ground problems.