Is this a guitar or a pickup question?

[Prawnik]

OK, long story, sit back.  I got a trashed vintage greybottom Strat pickup to install in the '69 hardtail Strat I built.  Sent the pickup to Tim for a re-wind, got it back, and installed it in the middle position (front a BK rewound Fender '69 RI, bridge a Tex-Mex sc)

The problem I am having is that there is a loud buzzing from the amp whenever I play the lower strings, only through that pickup.  Not only is it annoying, but it also keeps me from dialing in pickup heights.  

I re-soldered the pickup, so I don't think the problem is a bad solder joint.  Also, the old pickup I had before did the same thing.  

Any suggestions what this might be and how to fix it?

[indysmith]

it's neither a guitar or pickup question - this belongs in the 'tech' section :P
it sounds like some sort of grounding problem. If not it could be to do with the amp not being able to deliver those lower frequencies very efficiently