Help me with my grounding problem!


Junior Member
OK, so here's my grounding problem:

I have a two musicman pickup jazz bass.  Just got it wired up today.  The two musicman pickups each go to a series/split/parallel miniswitch, and then go to a gibson style 3-way.  From then on they go to a basic master volume and tone, and then to a mono jack.

All of the above works fine and as expected.  The big unexpected component is a shrill, loud buzzing hum that almost drowns out the bass tone.  The string ground may not be particularly effective in that I found the black bridge wasn't conducting particularly well (Schaller 463) according to my multimeter.  But what is strange is that there are only two things that silence the buzzing; touching the body of the cable plugged into the jack, or turning the tone pot down.  The tone pot is particularly interesting because it actually really silences the me, it isn't just cutting off the high end, the buzzing goes from veritable analog synth, sawtooth sine wave buzzing to silence by turning the tone pot all the way down, at which point I have a usable, if slightly dampened bass tone.

Anyone have any ideas?  I'd really love to get this thing up and running tomorrow so I can use it on Sunday, but if not I of course have a backup.  Just eager, that's all.  And yes, I suck at electronics, I know!  :D
Well, call me stupid, folks...

I spend all morning tinkering, improving the solder joints, fixing shortcuts that I didn't do cleanly, and generally doing things right instead of quickly, and I still can't stop the incessant buzzing and strange behavior (for instance, a shriek of hum when turning the volume pot, but only steady buzzing when all the way on).  So about an hour ago I realize, I am using this fancy new flushmount jack, and I check it with the multimeter...of course, I wired it backwards.  Once switched back everything sounds right, no more hum except a very mild bit when in split coil mode as expected.  The bass sounds fantastic btw.  But yeah, problem solved and lesson learned...if using a new part you are not familiar with, dig out the continuity tester and verify that it is wired the way you suspect!  I assumed the ground lug was the hot lug and vice versa.
It's a good lesson to learn though.  A shortcut now usually means a hassle later.  Take the time to do it right the first time, you won't regret it.  :icon_thumright: