gwertman
Rookie Solder Flinger
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Post by gwertman on Jan 29, 2007 14:46:32 GMT -5
40 dollars spent on shielding paint and shielded 2 conductor cable and the damn thing still buzzes when I'm not touching the strings. So - does anyone have any experience with this?
Situation:
Guitar: Lefty Ibanez style 6 string without pickguard - pickups are surface mounted and electronics are in back under cover plate Pickups: Bill Lawrence L500L in bridge, Dimarzio FRED in neck Switch: brand new Schaller P-switch megaswitch from stewmac.com Jack: Rapco Switchcraft Pots: Alpha 500K Shielding paint: lessemf.com CuPro Cote <.1 ohm resistance per square inch @ 2 mil thickness
The electronics cavity is painted with the shielding paint. I get continuity with a multimeter at every conceivable point inside here. Pickguard has that silver foil stuff on it. I didn't shield paint the individual pickup cavities though...
I have all the grounds going to the back of the volume pot. Except the ground for the L500L - that has to go to lug 2 on this switch for coil cutting reasons. But just that one. Then there's a wire from the switch to the back of the volume pot. Again, all grounds are going to the same place. Trem claw wire comes here too.
Shield wires from the pickups are going to back of vol pot as well. (You're supposed to put those to ground right??)
The wire from switch to volume, from volume to tone and from volume to jack are all 2 conductor plus shield with the shield attached at only one side as per stuff I've read at hamrony-central.com on shielding and grounding - evidently to reduce chance of ground loops. Yeah - I'm nuts to be using shielded wire in there since it sucks to work with but I want that damn buzz gone.
The jack cavity is not shielded - but the wire running through it is. Shield is connected to ground here and not at the volume jack side. Hell, even the cable to the amp is a Planet Waves custom double shielded cable... 25 freakin' bucks...
I have continuity from the strings to the ground at the jack so I know that the string bridge is in place.
Also, if I plug a guitar cable into the guitar I have continuity from the strings to the jack on the amp face. I'm assuming that's supposed to be that way.
Still - the damn thing buzzes. Also strange - I used those rubber tube type pickup height 'springs' from BL (you know the ones that look like orange shrink tubing?) to mount my pickup in the metal (gold plated brass I think) pickup rings and when I touch the pickup ring of the L500L the buzz gets louder. When I touch the pickup ring of the FRED (also gold metal but using regular springs for pickup height) the noise goes away similar to touching the strings. Also, I get no continuity from the BL's pickup ring to ground.... not sure what do make of that.
HELP! I'm going totally out of my mind! I've rewired this stupid thing 4 times now.
Thanks in advance,
Gary
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Post by sumgai on Jan 29, 2007 20:15:47 GMT -5
Gary, First, let me you to GN2, where we've all gone crazy, so you're in the right place! Your description is lengthy, so I haven't quoted it here, but I'm struck by two things you said. One, when you touch one of the pickup mounting rings, the hum gets louder, but touching the other pup ring acts normal - the hum gets quieter. The other thing is that business about the strings not quieting the hum when touched. You say you've got a good connection between the strings and the amp's input jack, but how good? Is it less than 1Ω? If it's higher, even just a bit (like 1½ or 2Ω), that's still enough to start suspecting a ground loop. And if you haven't heard that one before, then welcome to the land of esoteric electronics, where what you don't know will bite you in the butt. I would ask a trusted friend to take a look at your job. I really think that you've crossed a ground with a hot somewhere. In cases like that, your signal still goes out to the amp, but you get hum where you shouldn't. It can be insideous, true. Worse, it can even be the fault of a bad component, not necessarily your wiring efforts. But after re-doing this 4 times, I think you're too close to the trees, and can no longer see the forest. Back up, and use a second pair of eyes. If you have no friends close by, or they don't wanna do this for you, then take it to a good technician (who knows guitar wiring, not just something about electricity). Pay them if you have to, but I'm certain that the problem is gonna end up as a either a bad part, or an incorrect connection. Good luck! sumgai
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Post by UnklMickey on Jan 29, 2007 21:10:36 GMT -5
...The other thing is that business about the strings not quieting the hum when touched. ... i think you mis-read. he said: ... the % thing still buzzes when I'm not touching the strings. ... and really Gary, 2 percents in the same post? do you kiss your children with that mouth? .:lol:.
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Post by sumgai on Jan 30, 2007 2:03:14 GMT -5
unk, Right you are.... I picked up on the difference of the two pickup mounting rings, and his reference to the strings right there and then. I lysdexic'ed the two, and presto, instant error! OK, next tack.... ~!~!~!~ Gary, if touching your strings does quiet down the axe, then everything is working as designed. There will never be a 100% knock-out of all hum, we can only hope to reduce it down so low that we are no longer bothered by it when we've stopped playing. All you're really looking at now is the aspect of the mounting rings. That should be obvious to visual inspection, but you might also do a continuity check with your meter on both rings, and see where that leads you. FWIW, that factory-stock silvery stuff on the back of the pickguard is not necessarily the best quality, in terms of noise-blocking. I'd put some copper foil over it, the thought being that it's better to be safe than sorry. (2 mils of paint might be a bit much. ) Since you're experiencing more than common levels of hum, you'll probably have to shield the jack and pickup cavities too. I did, and I'm here to tell you, most guys think my amp isn't on, until I hit a chord. In short, if you put the effort (and dollars) into installing shielded cable, you shouldn't stint on the paint in the cavities. But that's just my opinion. And finally, yes, running all the shield/ground wires to one common point is the proper way to avoid ground loops and gives the best chance of reducing hum. HTH sumgai
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gwertman
Rookie Solder Flinger
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Post by gwertman on Jan 30, 2007 15:05:39 GMT -5
Thank you sumgai and unklmickey for your help with this. I've just put the second coat of copper paint in the pup cavities and will be grounding them tonight. I've checked continuity from all the places you could imagine and the grounds do not appear to be crossed with the hot anywhere.
Sorry about the language - I do kiss my kids with that mouth - but lately this project has wrecked my temper. It's amazing really. I do IT for a living - I should be used to frustration!
The pickup that buzzes more when I touch the metal pickup ring it's on is a Bill Lawrence L500L. He completely encloses his pickups in a plastic housing with no metal exposed. So for the dimarzio, the base plate of the pickup is connected to the pickup ring via the mounting screw. I touch the ring and it shunts noise through me or whatever. With the BL, I'm not sure what's happening there...
I'll also test for resistance from the strings/guitar ground to the nut on the input jack when I have it put back together and post that as well.
This paint is really cool by the way - after one coat it reads a resistance of 50ohms! Always assuming I'm testing that right - red and black leads touching painted surface 3 inches apart. Or is that the wrong way? Either way, my old shielding paint (the black stuff) never gave my continuity with the meter. But this stuff does. And it's water based and dries a really nice pale mocha copper speckle metalic color... maybe I can do a whole body in it!
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Post by UnklMickey on Jan 30, 2007 18:54:03 GMT -5
hey Gary,
i hope you know i'm not really offended by the percents, just wanted to give you a little bit of friendly grief. (with friends like that....)
tracking down hum can be frustrating, so we understand.
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gwertman
Rookie Solder Flinger
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Post by gwertman on Feb 1, 2007 16:24:16 GMT -5
Hey all, In between dealing with a PC CMOS/Hard drive error during a major hardware upgrade and the care and feeding of small children I finished shielding and rewiring my guitar The result? It's 90% quieter now with practically no hum! I can crank the rhythm gain to 7 and push the master volume on my 120 watt Peavey JSX to 5 without hum! (But I won't dare hit a chord - I'd kill any living creatures in a 10 mile radius!) HOWEVER - I still get that zizzzzz noise that goes away when I touch something metal. (It's half the strength of what it was though). This noise of course stops when I touch metal on the guitar that is part of the ground. Also - this noise goes away when I touch the input jack on the amp so the amp. Wonky amp maybe? (I haven't checked the resistance from guitar to instrument cord end yet... forgot till just now). Oddly enough, the zizz noise gets stronger the closer my hand is to the pickups. I guess I'm putting out gamma rays or something. This guitar had no shielding paint in the pup cavities at all unlike most that atleast have the black paint in there. Surface resistance from the bridge cavity to the ground at the output jack on the guitar is about 55 ohms! That's great shielding paint man - only two coats! So - thank you for all the advice and information. The internet is a great place sometimes full of cool people and usually decent info. This board is a great example of the free exchange of ideas and info. Oh, if anyone else is familiar with the zizzz noise let me know. Also, I'm gonna' post a sound clip sometime soon in case anyone wants to hear this noise and ID it. -Gary p.s. you know, I can't believe that this board replaces the word d.a.m.n. with a percent sign!! Sheesh...
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Post by sumgai on Feb 2, 2007 13:00:24 GMT -5
Gary, If it didn't, you can probably imagine what would get displayed on this, a family-oriented board that's supposed to be open to all ages. ;D The restrictions are a bit tight for my tastes, but better than the alternative, I hope you'll agree. The fact that touching any metal parts (including the amp's jack) quiets down the zizzzz is indicative of "All lights are green, we have a Go!" Everything is working as it should, and the final proof is, your body makes the pickups buzz as you approach them. Further refinement might show improvements, but the investment in time and trouble is up to you, of course. Is it? I dunnow, 55Ω sounds like a ground loop to me, but what do I know? Well, I do know that my copper foil has less than 1Ω from any point to any other point. I like to think that this leads to 99% hum reduction - my axe is so quiet that I have to look at the amp's pilot light to make sure it's on. HTH sumgai
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gwertman
Rookie Solder Flinger
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Post by gwertman on Feb 4, 2007 0:10:02 GMT -5
Heh - I agree about the language filter. I'm trying desperately not to let my kids hear me curse...
As for the 55 ohm thing - sorry, that was supposed to be 5.5 ohm. And since this paint reaches full resistance in 24 hours that number is now 1.5 - 2.8 depending on where I'm putting the leads. Still, under 1 ohm would have been nice. I think I'm gonna' get my money back and use copped tape from now on.
Still don't have that mp3 - but when I do I'd be interested to see what others think this noise is. What I call a zizzz others might call a hummm...
-g
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Post by sumgai on Feb 4, 2007 2:34:53 GMT -5
Gary, 1.5Ω to 2.8Ω isn't so bad, it's just not as good as copper foil that has less than 1Ω across the entire distance from the furthest pickup cavity to the output jack cavity. For purposes of hum reduction, I'd like to believe that the difference would be small indeed. But, who knows, that could be only part of a larger problem with a ground loop of some sort, I dunno. There is also the fact that shielding paint is composed of metal particles suspended in liquid. That presupposes that there may be an uneven coating all across the job surface, which will lead to 'holes' through which hum might leak into your axe. No matter how you slice it, the potential for voids like this is always present. That sound file might help, I'll wait for that before offering any more opinions. sumgai
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spud1950
Apprentice Shielder
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Post by spud1950 on Feb 5, 2007 8:52:01 GMT -5
"Gary, if touching your strings does quiet down the axe, then everything is working as designed. There will never be a 100% knock-out of all hum, we can only hope to reduce it down so low that we are no longer bothered by it when we've stopped playing."
"The fact that touching any metal parts (including the amp's jack) quiets down the zizzzz is indicative of "All lights are green, we have a Go!"
Sorry, but I don't understand these satements.If you have a hum or buzz that goes away when you touch the strings or other metal parts on the guitar,it's an indication that there is a bad ground somewhere. If all your grounds are properly connected, then this should not be happening.Maybe I'm missing something here!
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Post by sumgai on Feb 6, 2007 3:33:25 GMT -5
spud, Pardon me if I seem brazen, but I think that it would be for the best if I were to step aside, and let other members here fill you in on how that works. sumgai p.s. There's a quote icon in the toolbar above the message box - it's the second from right, bottom row.
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Post by UnklMickey on Feb 6, 2007 12:05:46 GMT -5
...Pardon me if I seem brazen, but I think that it would be for the best if I were to step aside, and let other members here fill you in on how that works. ... no problem. Spud, "You're just a big ole' Bucket O' Noise". read this:
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