earthing problem (baddass bridge?)

aviarybassist · #1 09-06-2007, 04:45 AM

hey guys i've got a problem with my squire jazz bass. i get a nasty buzz as soon as i turn the tone pot up. the buzz disappears when i touch the bridge or the strings. i get small amount of hum even when the tone knob is turned off, but i'm told this is normal.
i pressume it's an earthing problem but don't know how to go about sorting it. inside the bass, the pots look fine and there doesn't appear to be any loose wires. i have recently installed a badass 2 bridge and noticed the ground wire underneath the old bridge. is it possible that the badass is not contacting this wire properly? there did seem to be a small hollow underneath the bridge (with manufacture info engraved there) and the thought did cross my mind when installing it but i've played it since then and the problem didn't exist. i really want to elimate that option first as i don't want to have to take the bridge off only to realise it's a different problem. i bought the bass 2nd hand and haven't really used it before installing the bridge so i can't say if the problem existed previous to the installation, however i had no problem a week ago when jamming with some friends in my house, but i brought the bass into practice with my band yesterday and as soon as i turned my amp on i noticed the noise, fiddling with the knobs i soon realised it seemed to be related to the tone pot. my bandmates say there's a chance the problem may have to do with the fact that we all run our gear from various extension leads all coming from the same power source (the only power source in our rehearsal space) is this plausible?. we have a solder at our disposal but as i said before the wires all seem firmly connected. i'm pretty sure it's not a cable/lead problem but i've read that switching which ends of the cables you plug into the amp and guitar can help, but it didn't in my case. any words of advice?

ps. money is very tight and getting a guitar tech to look at it where i live will cost as much as 40 pounds

theshadow2001 · #2 09-06-2007, 05:36 AM

The buzzing is caused by radio frequency interference. The grounding is probably fine if the hum disappears when you touch it. What you need to do is shield the electronics as best you can. Do a search in pickups and electronics for a tutorial. I don't believe it to be too expensive a process if you do it yourself.

pkr2 · #3 09-06-2007, 09:43 AM

Check for continuity between the nut that attatches the input jack and the bridge.

If you dont have a meter, temporarily connect a short wire between the jack nut and the bridge. If the problem improves, recheck the connection under the bridge.

When you remove and replace a bridge, be sure to move the ground wire around a little bit so it doesn't set into the depression that becomes pressed into the body by the "clamped down" bridge mashing the wire into the wood.

BadMonk · #4 09-06-2007, 10:31 AM

Quote:

Originally Posted by pkr2

Check for continuity between the nut that attatches the input jack and the bridge.

If you dont have a meter, temporarily connect a short wire between the jack nut and the bridge. If the problem improves, recheck the connection under the bridge.

When you remove and replace a bridge, be sure to move the ground wire around a little bit so it doesn't set into the depression that becomes pressed into the body by the "clamped down" bridge mashing the wire into the wood.

What if the temp connect doesn't change or improve the probelm? What next?

pkr2 · #5 09-06-2007, 11:16 AM

Quote:

Originally Posted by BadMonk

What if the temp connect doesn't change or improve the probelm? What next?

Then further troubleshooting would be in order. About the bare minimum in test eqpt. for doing this sort of troubleshooting is a multimeter.

Troubleshooting AC hum, or ground loops is ranked right beside 'intermittent' problems in degree of difficulty in electronic diagnosis.

Luckily the signal chain circuit through a passive bass has been used for so long that everything that can possibly go wrong is already documented so it is pretty much "method repair", rather than actually measuring and testing. For instance, what the OP describes is a classic symptom with a classic repair.If grounding the bridge fixed the last ten basses with the OP's symptoms, chances are high that grounding the bridge will fix the eleventh one.

So, to answer your question: I would look for cold solder joints in the whole ground circuit. I would make sure that none of the wires in the control cavity are dressed too close to other wires. I would check the PUPs for balance between the PUPs. I would pull my hair and rant and rave. And curse.

Grounding the bridge will fix it, though! Betcha a cold brew. LOL

BadMonk · #6 09-06-2007, 12:26 PM

Quote:

Originally Posted by pkr2

Grounding the bridge will fix it, though! Betcha a cold brew. LOL

Thanks! I wasn't sure where to begin with fixing the problem. Had just been playing the bass with the buzzing sound in the background...but it's been getting more and more annoying. Now, I'll try this solution tonight when I get home. I'll let ya know about the cold brew. LOL. Thanks again!

theshadow2001 · #7 09-08-2007, 08:43 PM

I wonder how this worked out....

BadMonk · #8 09-09-2007, 05:56 AM

Well, I went home all set to do the troubleshooting that was kindly described by pkr2. Plugged everything and ... no buzz, no hum. Been checking every day since and still no unwanted noise (except for sour notes due to operator error).

Now, the noise would go away every once in a while but usually only for one practice session or less. Never this long... (I'm kinda glad but kinda not) I'm sure the noise will return.

pkr2 · #9 09-09-2007, 12:22 PM

Quote:

Originally Posted by BadMonk

Well, I went home all set to do the troubleshooting that was kindly described by pkr2. Plugged everything and ... no buzz, no hum. Been checking every day since and still no unwanted noise (except for sour notes due to operator error).

Now, the noise would go away every once in a while but usually only for one practice session or less. Never this long... (I'm kinda glad but kinda not) I'm sure the noise will return.

As I implied in my post ("Troubleshooting AC hum, or ground loops is ranked right beside 'intermittent' problems in degree of difficulty in electronic diagnosis."), intermittent problems are the hardest problems to diagnose because you can never really be sure that you've completely fixed the problem.

It's usually faster to resolder and tighten every ground connection in the circuit than it is to find the flaky one.

It's quite possible to get AC hum and all the ground circuitry be perfect. The phenomena is called a ground loop and basically is caused by stray current paths usually caused by such things as multiple ground connections attached to different points on a metal chassis. That's why star grounding, or one common point for all ground wires is common practice in audio circuits.

None of the above to be confused with single coil pickup hum. That's a hum problem that is designed into a lot of basses. Of course, humbuckers will solve the problem while minimizing the need for elaborate shielding.

Good luck with your problem.