sollipsist
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between the desert and the black muddy river
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Post by sollipsist on Jul 25, 2008 19:07:00 GMT -5
1st post, 1st time shielding, and probably a really silly question: I used heavy-duty aluminum foil throughout. Pressing the foil into the corners caused a few small tear holes (no more than 1/8"). Does this defeat the whole purpose, or will it ultimately not make much of a difference overall? I can always patch or cover the holes, if they are going to be a big problem... Oh, and for the jack cavity and rear tremolo cavity- is shielding essential or not? I'd certainly like to do everything that would make a noticeable difference...but if it's not necessary, I'd just as soon not breathe any more rubber cement fumes than I need to
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Post by ashcatlt on Jul 26, 2008 1:16:19 GMT -5
Thanks for stopping by. You'd ought to get some benefit even with the holes, but every little bit helps. The jack cavity doesn't normally get shielded but you could give it a try. Machphyst reported that his jack seemed to be shorting out when he shielded that section. There's nothing in the trem cavity worth shielding.
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macphyst
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Post by macphyst on Jul 27, 2008 10:13:01 GMT -5
Yes, my jack was shorting out when I would insert my cable into my guitar. I need to look into it some more but I believe what was happening is that the tip of my guitar cable was hitting the back of the cavity. I may go back and redo it if there is some way to adjust it to keep that from happening. If not, I'll leave it unshielded.
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Post by sumgai on Jul 27, 2008 12:02:09 GMT -5
Yes, my jack was shorting out when I would insert my cable into my guitar. I need to look into it some more but I believe what was happening is that the tip of my guitar cable was hitting the back of the cavity. I may go back and redo it if there is some way to adjust it to keep that from happening. If not, I'll leave it unshielded. A quickie, then I'm back outta here............. This "shorting when the cord is plugged in" problem comes to one's attention only when the cavity is lined with shielding, so manufacturers are not exactly noted for taking care to route the cavity to the full size it's supposed to be. The cure is obvious, according to them: don't shield that cavity. The proper cure is equally obvious, but much more troublesome - drill a bit of wood out of the "back wall" of the cavity, such that the prong on the jack can extend into that area without interference. Using a drill bit is dangerous to say the least - one slip, and Oh Mama Mia!, it's head-banging time. The better way to acccomplish this is to use a dovetail bit in a router. That way you can "undercut" some of the wood below the top surface of the guitar, and there's no chance of drilling through to the back side. This is the bit I'm speaking about, and a profile of what it does: Does this make sense now? Most of the time, the jack cavity doesn't really need to be shielded, but for those who want to be thorough, then here's how to overcome the "too small" bugaboo. ;D HTH OH, and sollipsist and macphyst, Welcome to the NutzHouse! sumgai
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macphyst
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Post by macphyst on Jul 27, 2008 12:40:39 GMT -5
Thanks for the welcome! And yes, removing wood from the inside of the cavity is the only thing I can think of as I don't believe there is any way to adjust the depth of a jack. Aside from drilling a small pilot hole for the screw of my grounding lug, I'm not going anywhere near my guitar with any sort of wood removing equipment. Heh! That's definitely something I'd leave for the professionals. With this being said, I'll stick with twisting the wires together to help with shielding. Although, last night I did find around here what seems like audio cable. It has a red and white lead surrounded by copper shielding and incased in the black wrap stuff. It has a 1/8" stereo plug on the end. I believe that's the size - it's the small one like earbuds have, for example. My only concern is that the 2 inner leads seem a little small. Close to the size of the leads in a telephone cable, possibly one gauge bigger. Does this size matter? I've read on this site before that someone had used telephone wire for other wiring purposes.
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sollipsist
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between the desert and the black muddy river
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Post by sollipsist on Jul 31, 2008 23:07:43 GMT -5
Thanks for stopping by. There's nothing in the trem cavity worth shielding. Thanks for having me Hmm...obviously, I'm still a blundering novice in this stuff...is there a quick and dirty explanation why the trem has to be grounded but it doesn't matter if it's shielded? Is that two entirely different considerations?
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Post by ashcatlt on Jul 31, 2008 23:57:17 GMT -5
As I understand it, the trem itself doesn't really have to be grounded. It has nothing to do with the electronics of the guitar.
The tremblock is a convenient place to make electrical continuity to the strings. The strings themselves have nothing to do with the electronics of the guitar, either.
But the strings are a very convenient place to make electrical continuity to the closest sorce of RFI/EM radiation to the instrument. Yep, that's you.
Shorting that big old transmitter to ground can sometimes help to reduce noise. If the pickups and wiring could be shielded perfectly, or if you'd be willing to tie a wire around your ankle and run it to a good solid ground point (please don't), there'd be no need for that bridge ground.
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Post by newey on Aug 1, 2008 5:50:23 GMT -5
Ash is right on the money here. As has been said before around here, the idea of shielding is to create a "Faraday cage" * completely enclosing the electronic components of the guitar. Shielding around non-electronic components accomplishes nothing. On Strat- style gits, the string ground is often run from the trem claw rather than from the trem block. Most trem claws have a little nubbin in the middle for just this purpose, it's just easier to get a good solder connection to that than to the block. The strings are then grounded through the trem springs to the block, and thence to the bridge and string saddles, and thus to the strings. "String ground" and "bridge ground" are used interchangably to describe this connection. *Named after Michael Faraday, whose name also gives us the "farad". That's true immortality, when one has a unit of measurement named after oneself.
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sollipsist
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Post by sollipsist on Aug 1, 2008 11:10:24 GMT -5
Ahhhh! Therefore (as long as it's continuous), I would get the same benefit from grounding the bridge instead? Since the pickguard butts right up against the bridge, I could extend the foil shielding from the nearby bridge pickup cavity area...one could even put the bridge screws right through the foil. ...might be less frustrating than trying to solder to that claw thing- I have no such nubbin on mine, just a rusty-looking burn mark
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Post by D2o on Aug 1, 2008 14:47:17 GMT -5
Ay, yes. The "Riverdance" guy.
Yes ... and yes, electrical and magnetic continuity are key to shielding.
Hmmm, seeing as the QTB instructions call for the wire from the tremolo to be attached to the shielding at the bottom of the cavity, I think your method may have some merit ... although I've not tried it that way. I dunno? ... try it and see?
Personally, I'd rather use a wire from the bridge or tremolo. What if you file the rusty burn mark down a bit for traction?
One time I just couldn't get the wire to stay soldered (!) and eventually just wrapped a wire around one of the screws holding the bridge down instead ... I was desperate and it was better than nothing.
DD
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Post by newey on Aug 1, 2008 19:13:05 GMT -5
DD- Many Tele bridgeplates are grounded thusly. With a Strat trem (of vintage type) you might have issues if the player in question liked the trem adjusted loose and dive bombed repeatedly. And Sol- So think green and recycle it. As DD suggested, judicious application of some friction, it'll be ready for a solder joint. In short, you should run the wire. Usually, there's a hole between the front and rear routes specifically so you can run that wire. I think trying to run the ground through your cavity shielding sounds problematic, although I confess, I don't have a good explanation of Why Not? . . . And DD- ROFL . .etc. ;D ;D
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Post by ashcatlt on Aug 1, 2008 21:48:17 GMT -5
I worry that you might find that either the screw or the chrome plated bridge gives less than ideal conductance. Have you, or do you intend to, installed all 5 springs? Most folks have a couple of little tabs available for soldering.
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sollipsist
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Post by sollipsist on Aug 2, 2008 9:25:53 GMT -5
That's a good point- the bridge and trem block don't strike me as ideal conductors. I do have all 5 springs in, but I'm sure I can make the claw work (thanks for the filing tip).
I am curious about the ground path, though...in the instructions, I see a ground running to the low terminal on the volume pot...and then a jumper to the star ground. Wouldn't this be redundant if the volume pot is also grounded to the foil on the pickguard?
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Post by D2o on Aug 2, 2008 10:41:56 GMT -5
Good question.
I think the jumper you mention merely replaces the one that went from the terminal to the back of the pot, where the pickups were grounded before.
Now they all go to the star ground, which is insulated from the actual shielding chassis.
As an aside, the wires between the backs of the pot cases are removed because they would be a ground loop - which sounds ominous ; I like your term better ... "redundant", which I think is closer to the truth.
DD
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Post by ashcatlt on Aug 2, 2008 12:34:55 GMT -5
Yeah, that lug needs to hit ground somewhere. If you don't run the wire to the star ground and also don't run it to the back of the volume pot, then it goes nowhere. It would not technically be a potentiometer anymore, but rather a variable resistor, and you won't get much in the way of attenuation out of it. It definitely won't go all the way off when you turn it down.
The pot's case is grounded by way of the shielding, allowing it to act as a (somewhat redundant) shield for its own innards. Note that there is no internal connection from any of the lugs to the metal case, or body of the pot. This case is separated from the signal ground so you can use the safety capacitor to isolate the amp ground from the metal parts of your guitar.
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sollipsist
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between the desert and the black muddy river
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Post by sollipsist on Aug 3, 2008 12:51:59 GMT -5
Update- all the work is done, now for troubleshooting The pickups and controls are all working as they should. I'm proud of that- this is my first complete re-wire. Aside from noise issues, the guitar sounds wonderful...this 20-year old Mexican-made Strat now sounds as good or better than most top-of-the-line new USA-made Strats. Big difference in volume settings- I seem to drop about 50% going from 10 to 7, so I may replace it with a linear pot if I find that I need more range. I was prepared to replace the 250k pots with 500k pots, but brightness doesn't seem to be as much of a problem as I expected using the Texas Specials. I am still getting a little too much noise in all settings...the noise actually increases in positions 2 and 4, so it must not be (solely) single-coil hum. I suspect contact with shielding is the issue (maybe that trem wire isn't connecting properly).
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Post by ashcatlt on Aug 5, 2008 11:54:40 GMT -5
I'm not sure what to tell you about the volume thing. Maybe you could adjust the taper with a resistor or two, but I'm not the best person to tell you exactly how to accomplish that.
The fact that you're getting more noise in 2 and 4 means you've got 2 coils (M+(N or B)) contributing to the noise. Are you sure that the middle pickup has reversed magnetic polarity to the other two? You can test it by trying to push the pole pieces of the middle pickup onto those on one of the others. If they stick you're good there, and the noise means you've wired the middle pickup backwards. Does it sound especially thin or phasey in those positions?
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Post by D2o on Aug 5, 2008 12:28:40 GMT -5
I'm not sure what to tell you about the volume thing. Maybe you could adjust the taper with a resistor or two, but I'm not the best person to tell you exactly how to accomplish that. The fact that you're getting more noise in 2 and 4 means you've got 2 coils (M+(N or B)) contributing to the noise. Are you sure that the middle pickup has reversed magnetic polarity to the other two? You can test it by trying to push the pole pieces of the middle pickup onto those on one of the others. If they stick you're good there, and the noise means you've wired the middle pickup backwards. Does it sound especially thin or phasey in those positions? I'm with ash - a little stumped. If it was a case of incorrect polarity or something, there would be a weak, "tinny" sound in the 2 or the 4 ... but I don't think there is a combination that could cause that in the 2 and the 4 position*, so it must be something else ... ... but I dunno what. DD * (this assumes that your Texas Specials have the same layout (polarity/position) as a set of stock pups does ... but maybe you have all three of the same polarity?)
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sollipsist
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Post by sollipsist on Aug 8, 2008 9:56:04 GMT -5
Nope, I don't hear any drop in output in the 2 and 4 settings...the tone is slightly quacky, but not enough to make me think it's out of phase. I'm nearly certain the wiring is correct; everything sounds as it should, except for the noise.
I do get some nasty squealing feedback with high gain- the first thing that makes me think of is microphonics.
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sollipsist
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Post by sollipsist on Aug 13, 2008 12:18:13 GMT -5
In case anybody cares, the experiment worked fine; grounding to the bridge works just as well as running the trem wire. I used a strip of foil from the bridge p/u cavity; no soldering, no extra wires, and you can't even see it once the pickguard is back on.
I use a standard trem with all 5 springs pulling it flush (I would have replaced it with a hardtail, but I didn't want more screwholes). I don't know that my method would work as well with heavy trem use.
There is almost no noise now- I have to max everything on my amp to hear any hum at all. I've heard noisier humbucker guitars. The Texas Specials ended up being quieter than the Lace Sensors they replaced (and sound much better, IMHO).
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Post by D2o on Aug 13, 2008 12:27:08 GMT -5
Awesome! (I guess that means someone cares ;D ) But ... fill in the blanks for me: was it the shielding to the bridge experiment that got you from here: to here: Was it just improper bridge grounding that was troubling you, or was there more to it? DD
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sollipsist
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Post by sollipsist on Aug 14, 2008 13:00:28 GMT -5
Oops, there WAS a little gap in the tale Yes, it was definitely a grounding issue- my advanced testing equipment (i.e., my finger) confirmed the nature of the problem. My practicing environment is VERY noisy- basically sitting on top of flourescent lights in between three PCs on a wireless network. Still unsure why it would be worse in positions 2 and 4...but even with unshielded overwound pickups, the extra foil strip cleared everything up beyond my wildest hopes.
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Post by D2o on Aug 14, 2008 13:10:31 GMT -5
... lucky ... my advanced testing equipment usually causes more problems than it solves ... [/size]...but even with unshielded overwound pickups, the extra foil strip cleared everything up beyond my wildest hopes. [/quote] Yeah, that's the part that still confuses me. Oh well, it works now - for whatever reason - and that's worth a shrug and a smile . Good stuff! DD
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