deadleg
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Post by deadleg on Nov 29, 2013 11:07:27 GMT -5
Hi everyone, I checked out the Guitarnuts page on shielding as I was looking into this stuff so thought this might be a good place to register and ask about the issue I'm having here. Google as I might, I can't find quite find the same problem. The input jack on my Squier Jazzmaster got slightly loose and crackly so I figured while I was looking into that I'd change the pickguard and shield everything as best I could with copper shielding (the conductive adhesive type in the cavities and just a sheet of the regular stuff on the guard). With this done I loosely put everything back together, plugged in and set some high gain to see if everything seemed to be working OK, as far as I could tell without any strings on at least! What I got was this: Neck pickup selected = Hum Both pickups selected = Pretty much the same amount of hum as above Bridge pickup selected = Very little hum which quietens further upon touching anything metal apart from the bridge pickup magnets which amplify the hum to about the same level as above As far as I'm aware the pickups were behaving normally prior to my opening it up, with the neck pickup a little hummy, the bridge pickup hummier still and the middle position hum cancelling. Obviously I wasn't expecting the 60 cycle hum to go by shielding the guitar, it's just that its behaviour seems to be suggesting that something's out of whack. I haven't altered the main electronics in any way, everything was grounded to the back of the volume pot which was then grounded to one of the bridge thimbles which is how I've left it. The only other thing is that there were two 'ground' leads screwed into the painted body cavities under each pickup even though I've read elsewhere that the paint on these isn't actually shielded, which seems quite odd. Just out of experimentation I've tried screwing those two leads into the shielded body where they originally were, one at a time, both together and them both covered so they're not in contact with anything, all with the same result. Seemed like it would be a pretty simple task but obviously things are always simple until the unexpected happens and I'm not knowledgable enough on electronics to know what else to try. Apologies if my description isn't up to snuff, I'll do my best to solve that if you can prod me in the right direction. I did take some pictures but I'm not sure how much use they'll be as the wiring seems pretty messy in these things: i.imgur.com/qFtrVlM.jpgi.imgur.com/RljDZD7.jpgi.imgur.com/dQl6pIk.jpgi.imgur.com/eISsu8J.jpgAny help most gratefully received
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deadleg
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Post by deadleg on Nov 29, 2013 13:27:00 GMT -5
Quick update having investigated a bit further and Googled some more. Although it's very awkward to see, it seems as though the two shielded wires going from the input jack and the volume pot into the pickup circuit are grounded at both ends. Looks like it'd be quite a job to undo for someone with my limited soldering skills unfortunately.. Does that sound like the likely culprit here?
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Post by ashcatlt on Nov 29, 2013 13:44:43 GMT -5
I don't see anything wrong in there. In fact, it looks like a pretty nice job. You didn't actually change any of the wiring? Just pulled everything out intact, shielded it, and put it back?
First, it should get quieter in all positions of the switches when you touch something metal like the bridge or the barrel of the cable. It also should (usually) get noisier when you touch the pole pieces in the pickups. The worst and closest source of noise to the guitar is you. When you touch the bridge, you essentially short yourself out. When you touch the pole pieces you focus your noise right into the middle of the pickup coil where it can do the most damage.
I suspect the validity of the test itself. You said that you "loosely" put everything back together. There might be an issue with continuity between the pickguard and the cavities if the pg isn't actually screwed down. Course the wires should take care of that...
You also said that you don't have any strings on it, and that you plugged it into some "high gain", by which I take it you mean a bunch of distortion*. This, I think, is where your issue is. You are never going to get rid of the noise. What you're looking for is to maximize the difference between the desired signal (from the strings) and the unwanted noise. Without strings you have no way of judging that difference. With a whole lot of distortion, pretty much everything that goes in will come out about the same volume anyway.
And I don't really trust your memory of what it was like before. If you had carefully tested and measured the noise prior, and them come back after and used the exact same settings to test again, we could compare, but...
Put some strings on it and plug it into something clean and get a real feel for the S/N ratio.
* It's common usage, but gain != distortion. Distortion comes when the circuit tries to add gain and fails for one reason or another.
Oh, and thanks for stopping by!
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Post by newey on Nov 29, 2013 14:32:30 GMT -5
deadleg-
Hello and Welcome to G-Nutz2!
I'll second what ashcatlt said- report back after you've strung it. A test run with things "loosely" together is fine if you're checking to see that a new wiring works as intended, but for evaluating noise, there's no substitute for buttoning everything up and playing it.
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deadleg
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Post by deadleg on Nov 29, 2013 16:03:49 GMT -5
Thank you both for the responses So neither of you think the wires grounded at both ends could be the culprit? Is that normal? My knowledge on this stuff is sketchy at best as I'm sure you can tell! Sorry about the lengthy reply and the formatting below but I'll try to be as detailed as possible! I don't see anything wrong in there. In fact, it looks like a pretty nice job. You didn't actually change any of the wiring? Just pulled everything out intact, shielded it, and put it back?Yes, just the above aside from adding a bit of electrical tape to tidy up the wire bunches as you can see in the photos. The only things I had to touch were those two screwed-in ground leads which I've tried in every configuration just in case I was missing something there (there's also another lead that goes through to ground the bridge thimble but I haven't touched that). First, it should get quieter in all positions of the switches when you touch something metal like the bridge or the barrel of the cable. It also should (usually) get noisier when you touch the pole pieces in the pickups. The worst and closest source of noise to the guitar is you. When you touch the bridge, you essentially short yourself out. When you touch the pole pieces you focus your noise right into the middle of the pickup coil where it can do the most damage.Sorry, I'll re-word and elaborate a bit more as I should've done originally and say how they behaved before too in brackets. This is with the two mystery ground lugs screwed into the body (doesn't seem to matter if it's either or both but with neither attached the bridge pickup position behaves even more erratically while the others stay more or less the same). Neck pickup ('normal' level of hum before, didn't notice much of an effect from touching strings, metal etc.) - Quite a loud, strong buzz with a harder sound. Touching metal points adds another, quieter sound but touching the pickup poles doesn't seem to affect it. Middle position ('hum cancelling' to a large degree before, didn't notice much of an effect from touching strings, metal etc.) - Pretty much the same as above, though touching the bridge pickup adds the same, quieter sound that touching the shielding etc. produces above. Bridge position ('normal' level of hum before, didn't notice much of an effect from touching strings, metal etc.) - A much quieter, more 'normal sounding' hum which quietens further when touching metal, apart from the bridge pickup poles which produces a much louder radio interference sort of sound. I suspect the validity of the test itself. You said that you "loosely" put everything back together. There might be an issue with continuity between the pickguard and the cavities if the pg isn't actually screwed down. Course the wires should take care of that...You may well be right , I screwed in a couple of the pickup screws on each one and screwed the guard in in a couple of places (the new pickguard wasn't a perfect fit so I didn't want to start on new holes until I was confident I was about done) and pressed the other spots down as best I could. I would've tried properly reassembling everything if it weren't for the fact that the pickup behaviour seemed so far off.. I'm pretty confident it's not right. You also said that you don't have any strings on it, and that you plugged it into some "high gain", by which I take it you mean a bunch of distortion*. This, I think, is where your issue is. You are never going to get rid of the noise. What you're looking for is to maximize the difference between the desired signal (from the strings) and the unwanted noise. Without strings you have no way of judging that difference. With a whole lot of distortion, pretty much everything that goes in will come out about the same volume anyway.
And I don't really trust your memory of what it was like before. If you had carefully tested and measured the noise prior, and them come back after and used the exact same settings to test again, we could compare, but...Yes, sorry I did mean a distortion pedal. Well, a virtual one as I'm using Guitar Rig at the moment which is why I'm pretty confident on the before/after differences as they stand because I just loaded up a preset I'd been using before.. Same volumes, gain etc. I know shielding it won't get rid of the 'normal' hum that was there before but this is like a whole different level, if it was just that I'd be thinking something was amiss but the odd pickup behaviour into the bargain just compounds it. If the middle position cancelled the any of the noise it'd all make a bit more sense to me. Put some strings on it and plug it into something clean and get a real feel for the S/N ratio.
Will get straight onto that but what do you think I should do with those two ground leads that were screwed into the unshielded body originally? Screw them into the body together, apart or leave them out entirely?
Thanks again for the help here, a job I thought would take a couple of hours has already turned into a couple of days!
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Post by ux4484 on Nov 30, 2013 2:32:25 GMT -5
Welcome! I would suspect Fender has extended it's "shielding paint" to the squier line. Was the cavity black with a grainy texture to the paint? If so, it was their shielding. The electrical connection to this is spotty at best, but now, with the foil inside, at least one of those leads will ensure the guard is connected to the cavity shielding when buttoned up. Or you can make a couple of nice lips of foil over the edge of the cavity where there is clearly room for it under the guard. Also, which bridge do you have? (Those two bridge holes could be for either the trapezoid or the TOM/Jaguar Trem). Is there a ground lead from the bridge? if it's the two piece, Is there a lead from either? Both? Some of the Fender badged Blacktop and Modern Player models have been missing these leads, and it can cause all kinds of fun. In my case, the pickguard made a "whooshing" noise when my pinky would brush against it after a strum. After drilling/feeding a ground lead from the bridge, my problem was solved (Blacktop Telecaster).
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deadleg
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Post by deadleg on Nov 30, 2013 5:41:47 GMT -5
Hi there, thanks for that Yeah it was the black gloopy stuff. I started all this without a multi-meter figuring it'd be a quick and straightforward job so I couldn't test it myself but I've read in a few places people saying it's literally just paint and required proper shielding.. They could well be wrong obviously but I guess doing the copper tape thing on top shouldn't hurt in any case? I did ensure the foil went over the edges cavity edges slightly where it wouldn't be seen and also the larger area between the pickups so there should be a lot of contact, especially with either or both of those ground leads screwed in (am I right in thinking either or both screwed in is fine but neither probably isn't the best idea?) The guitar comes with a version of the regular, somewhat problematic Jazzmaster bridge but I've just had a Staytrem upgrade arrive too. There's a lead going through the body connecting the back of the volume pot to the nearest thimble which I've just left alone. I couldn't tell you if there's another lead going from one thimble to the other but I assumed with the bridge in it'd do the same job anyway? I've tried testing it with the bridge in and out along the way in any case.
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Post by ux4484 on Nov 30, 2013 8:11:52 GMT -5
Then, It sounds like that was your body central grounding point ala Fender. Your bridge ground sounds ok, If all else is good, you should only need one of those redundant leads now (just in case your foil does NOT touch) As Ash and newey said, you'll need to button it up tight and string it to REALLY test it.
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deadleg
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Post by deadleg on Nov 30, 2013 8:24:52 GMT -5
Right then, thanks. I'll screw both those wires in so as not to make any permanent changes for the time being and get it properly assembled!
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