pateo
Rookie Solder Flinger
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Post by pateo on Jan 29, 2010 6:40:46 GMT -5
I was working on my guitar last night, trying to get rid of an annoying hum. I assumed that I had some bad wires/wiring making the guitar not completely grounded.
Whenever I touched the strings, the hum got louder. Whenever I touched the tone or volume pot, the hum got softer. So I figured the controls and the bridge weren't connected. Consequently, the bridge/strings not grounded. To my surprise it was. So the guitar, to my knowledge, was completely grounded.
Long story short, I got frustrated to the point that I yanked out that ground wire that was connecting the controls and the bridge. The hum stopped and the guitar played fine. I can not explain how this happened. Doesn't this mean that the bridge via the strings aren't grounded? My best guess is that the ground wire was somehow making some sort of ground loop.
If anyone could kindly explain this phenomenon, it'll make my day. Thank-you.
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Post by newey on Jan 29, 2010 6:56:07 GMT -5
Pateo-
Hello and Welcome!
I have no explanation for this, but I'm sure others will weigh in.
It does mean, presumably, that your bridge/strings aren't grounded, unless your particular guitar offers an alternate route to ground. Since the bridge ground isn't in the signal path, any theoretical ground loop there shouldn't matter.
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pateo
Rookie Solder Flinger
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Post by pateo on Jan 29, 2010 7:16:46 GMT -5
Thanks for the warm welcome Newey.
I've read few people having similar problems on the web, and one of my friend is suffering from the same exact problem. I just wanted to make sure I knew what was going on before I start going yanking out grounding wires from every guitar.
The guitar I was working on has active pickups on them, and I thought that could be what's causing this. However, the friend previously stated has passive pickups.
I've looked to see if there were any alternate route for ground, but the bridge I'm using is a solid state, not a tremolo, so there's no access to it besides the tiny hole leading from the control cavity to the bottom of one of the posts on the bridge.
Lastly, the hum I was trying to get rid of most likely was a 60hz, since my tuner was picking up frequency between B and B flat. (made it very hard to tune normally)
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Post by newey on Jan 29, 2010 8:48:14 GMT -5
Someone here recently noted that EMG advises disconnecting the bridge ground with their active pickups, although no one seemed too clear on what the reasoning would be. But maybe that's a clue here.
Your friend could be having a different issue altogether.
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Post by ashcatlt on Jan 29, 2010 13:06:35 GMT -5
Who did the wiring in this guitar? Is it stock from the factory, or has it been modified? Did it come with actives to begin with, or were hey installed aftermarket? Where did the "ground wire" from the bridge attach to the circuit?
Were you standing in a puddle of beer on a concrete floor?
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Post by D2o on Jan 29, 2010 15:19:48 GMT -5
Were you standing in a puddle of beer on a concrete floor? I can't believe newey missed that.
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Post by sumgai on Jan 29, 2010 17:42:39 GMT -5
ash, you've got to be the cruelest Nut on this forum! ;D pateo, don't pay him any attention, he's just miffed that you didn't get shocked like he did, and ever since then, he's been trying to lure newbies into falling for the same stunt he pulled. and D2ooie, newey missed it because he's still stuck in his bomb shelter, where beer ain't allowed (cause it'd instantly get diluted what with all the dampness seeping through the 50 year-old walls). Then again, I should talk, eh? Oh, and pateo again..... Hi, and to the NutzHouse! sumgai
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Post by ashcatlt on Jan 29, 2010 19:41:48 GMT -5
Actually, I was thinking that if he was coupled to the floor, which was coupled to the amp's safety ground, there might be a ground loop there, though it's not likely.
The other questions I asked are valid, though.
It would make plenty sense if the wire from the bridge was somehow (incorrectly) connected to the hot output.
I'm wondering, too, if it's possible that his (body) noise could be contaminating the power supply for the active circuit. Since this circuit "expects" to get relatively clean power from a battery, it might not have much power filtering.
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pateo
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Post by pateo on Jan 30, 2010 4:16:32 GMT -5
Thanks for all the input, and usually I don't find myself drenched in pool of beer until Sunday morning.
The phenomenon does seemed to be caused by the active pickups. The wiring on the guitar is mostly stock. The only thing installed afterward was the pickups. I checked and made sure the polarities weren't reversed.
The ground wire from the bridge (which is now disconnected) used to be connected to the flat surface of the volume pot. This was also strange to me since, I thought connecting the wire to the tone pot would make the ground circuit shorter. (Tone pot is closer to the output jack on my guitar.)
I've yet a lot to learn about wiring guitars and will still do some poking around the web to see the cause of this. Until then I hope I won't get shocked by this psuedo grounded guitar.
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Post by newey on Jan 30, 2010 8:24:11 GMT -5
The difference in distance is so short as to be meaningless. One grounds to whatever is handiest.
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