|
Post by axekicker on Jun 15, 2010 12:39:33 GMT -5
I've come across this term while researching, and I'm wondering what, exactly, it means. I think I may have this problem as I've recently installed a humbucker into a project guitar and the hum is worse than a single coil. This is a very basic 1-pickup, 1-pot EVH style guitar, and I've had nothing but problems with it. Meanwhile, I've had lots of success wiring 3-pup super strats and the like. But for whatever reason, this "simple" project has been nothing but a noisy pain in the butt as I've blown out two pots already just trying to get the solder to stick. One step forward, two steps behind and so it goes. Thanks for the help as usual!
|
|
|
Post by ijustwannastrat on Jun 15, 2010 13:01:09 GMT -5
Do you feel like throwing your schematic that you are using up on the board? I'm guessing it's pretty simply, but so am I, in addition to being a "visual learner".
As for soldering to the pot, somebody recently posted a link to ring terminals that are easy to solder to, rather than the case of the pot, but I can't find it. MUST LURK MOAR!
Oh yea, I don't know more than this: GROUND LOOP = BAD I think that with a single HB and pot, your chance of ground loop is REALLY low. But as I understand, it's something along the lines of sending the HB's ground wire to the pot, the pot to the jack, and the jack to the HB. But please don't take my word for it...
|
|
|
Post by ashcatlt on Jun 15, 2010 13:27:54 GMT -5
A ground loop is a redundant ground connection. Any time you've got a a node in your circuit which is connected to ground via more than one route, you've got a ground loop.
I think that we have pretty much decided around here that the idea of a ground loop inside a guitar is not a real concern. They can't really be big enough to cause noticeable noise, and the voltages are very small.
Where you really need to worry about ground loops is when connecting various active components in your rig. If you've got two amps, for example, plugged so that the sleeve of the jacks connect - that's one ground connection. Then, they're plugged into the wall and the 3rd prong "safety ground" connection from the two amps meet each other somewhere along the line. That's another ground connection. And that's a ground loop.
Likewise, if you've got a pedal plugged into a wall-wart, and your running a cable to your amp, there could be a redundant ground connection there.
I'd imagine there's something else going on in your guitar. Have you shielded it?
|
|
|
Post by D2o on Jun 15, 2010 14:50:12 GMT -5
The point about “redundant” grounds is that, if you are having hum issues, it’s likely to be from “lack of” proper grounding rather than “too much” grounding (“so to speak”, i.e. I routinely run redundant grounds in shielded guitars, with no hum issues).
I have only ever had a problem like you’re describing on two occasions:
1) I forgot a wire between the backs of the pots 2) I accidentally reversed the wires to the output jack (see correct wiring in Wolf's reply to your question about volume pots)
EDIT: … I may have had a bridge ground problem once, as well ... I can’t remember – anyway, that’s another possible culprit.
As ash says - and JohnH, too - it’s best to avoid soldering to the backs of the pots, if possible.
However, it’s not always possible, so if you must solder to the back of the pots, here is how I have always done it – and I’ve yet to have any kind of problem (as copied from previous posts):
I have a 25 watt iron - which works just fine, and I like to use the thinnest electronic rosin core solder that I can find.
Make sure that you allow your iron to properly heat up for at least 5 minutes, that you always keep the tip of your iron clean, and that you tin it (melt a thin layer of solder on the tip).
When I am soldering to something like the back of a pot, I lay the side of the tip of the iron on the surface to be soldered to for a good 30 seconds before placing the wires that are to be soldered to it on the surface and then laying the side of the tip of the iron on the wires that are on the surface for another good 30 seconds or so.
Then I press the point of the tip of the iron on the wires, and make sure I've got ample solder to make a huge honkin' glob of solder on a fairly hot surface, so that I have the best chance of getting a good and durable solder connection. I have never damaged a pot doing this - although that could happen with a much more powerful soldering iron, so best stick with about 25 - 40 watts.
D2o
|
|
|
Post by chuck on Jun 15, 2010 18:57:06 GMT -5
it is easier to heat the edge of a pot than it is the center. you wont have to hold the iron on the pot as long if you solder on the edge.
|
|
|
Post by JFrankParnell on Jun 15, 2010 22:51:51 GMT -5
I'm a terrible solderer'er but the cheap butane iron from radioshack has been working real well for me. Also, this little can of tip cleaner is great: www.radioshack.com/product/index.jsp?productId=2062721 you dip your tip in it to keep it clean and hot. Seems like that helps alot for me. Then, on the pots, I do an obviously bad job at first, but then just hold the tip right on the edge till you see the solder 'run'. Also, I was thinking that it might work to put a ring terminal on the wires and connect that under the pg, between the pot and the pg. Furthermore, if you have a good shield on the back of the pg, wouldnt that create a ground between the pots, etc? Or one strategically placed strip of copper tape?
|
|
|
Post by ashcatlt on Jun 16, 2010 0:05:00 GMT -5
Also, I was thinking that it might work to put a ring terminal on the wires and connect that under the pg, between the pot and the pg. Furthermore, if you have a good shield on the back of the pg, wouldnt that create a ground between the pots, etc? Or one strategically placed strip of copper tape? This is exactly what's suggested in the QTB instructions. The pot shells connect to each other via the shield, and the shield connects to the star ground for the rest of the circuit via a wire connected to a ring terminal around the shaft of one of the pots under the pickguard, where it contacts the foil. D2o (and a couple others) have reported instances where there was still some noise with this setup, and they were forced to run wires between the pot shells themselves. This could be done via ring terminals as well, of course. I don't know why this would be necessary as long as there's good conductivity through the shield, but ChrisK used to admonish us to never trust a shield to carry signal (even noise).
|
|
|
Post by axekicker on Jun 16, 2010 2:06:25 GMT -5
Thanks for the replies. I will be referring to Wolf's schematic and starting from scratch with a proper pot. I'll also lay down some copper foil throughout. If that doesn't work, I'll post pics and get more feedback. Thanks, guys.
|
|
|
Post by newey on Jun 16, 2010 5:22:12 GMT -5
Keep in mind that any shielding must be grounded to be effective. The pieces must be electrically continuous, and they all have to reach ground at some point, whether through a ring terminal over a pot shaft or whatever.
|
|
|
Post by D2o on Jun 16, 2010 9:59:49 GMT -5
Yep, that is the true QTB – and it really does work best. However, remember my shielding experiments here? (you remember that urthman stuff ash found?) They were done with continuous shielding, yes … but the guitar was not star grounded, nor was the shielding attached to ground (not deliberately, anyway). Part of what I was trying to do there was compare a “stock” shielded guitar to a “stock” unshielded guitar – no QTB star ground, or cavity screw ground … just the most basic “Faraday Cage” type of deal. If the pots were touching the shield and causing redundant ground, it was not by design. The QTB mod is the best method to follow, but I think it is important to mention that the benefits of shielding can still be realized, even without the full QTB, and even if the guitar remains “stock” wired. Basically, from least effective to most effective shielding: Least reduction of hum: slap a bunch of aluminum tape in your cavity and on your pickguard - so everything is covered, without worrying about continuity Moderate reduction of hum: carefully shield the cavity and pickguard with aluminum tape, ensuring shield continuity Better reduction of hum: apply the QTB mod, using aluminum tape Best reduction of hum: apply the QTB mod, using copper So, “your mileage may vary” definitely applies, and you should aim for the QTB mod, done properly and following newey’s advice ... ... but, no matter how you shield, you should notice at least some reduction of hum. D2o
|
|
|
Post by axekicker on Jun 16, 2010 16:02:41 GMT -5
I've read here, and in other articles, that you need to be "continuous" or have electronic continuity. What does that mean, in this context? I have a multimeter, but what am I looking for in terms of readings? Thanks.
|
|
|
Post by newey on Jun 16, 2010 16:20:29 GMT -5
I mean that the various pieces of shielding foil should be electrically connected, one to another. You can check it with a multimeter from farthest point to farthest point, horizontally and vertically.
Keep in mind that, unless you're using the copper tape with conductive adhesive, most glues aren't conductive. So simply overlapping pieces of foil with glue won't ensure a connection.
The original QTB mod advises folding the edges of the foil over where they meet another piece, and taping the overlap down. I've used that method with good results.
|
|
|
Post by ashcatlt on Jun 16, 2010 17:23:40 GMT -5
I've read here, and in other articles, that you need to be "continuous" or have electronic continuity. What does that mean, in this context? I have a multimeter, but what am I looking for in terms of readings? Thanks. You're looking for very close to 0Ω resistance between any two points on the shield and also between any point on the shield and the jack sleeve. If your meter is not auto-ranging, make sure you set it to it's lowest DC resistance setting.
|
|
|
Post by sumgai on Jun 17, 2010 14:08:19 GMT -5
I've read here, and in other articles, that you need to be "continuous" or have electronic continuity. What does that mean, in this context? What you're learning here is why copper is better than aluminum. Yes it's more expensive, much more so, but in terms of electrical continuity, there's no comparison. Whyzat? 'Cause you can't solder aluminum. (Well, at least not in a guitar-mod scenario....) Take a look here: See where I've soldered the pieces of foil in several places to ensure electrical continuity? That's what separates the men from the boys, when it comes to making almighty sure that you're doing the most possible to get the job done, instead of "just enough to get by". (newey's assertions above notwithstanding.) Taking your meter and probing any spot in there, compared to the ground terminal on the output jack, will read between 0.2 to 0.4Ω. But for practical purposes, and because not everyone can afford to calibrate their meter to NIST standards every year or so, it's commonly accepted that if your readings are less than 2Ω, then you're pretty much good to go. HTH sumgai
|
|
|
Post by chuck on Jun 17, 2010 14:52:10 GMT -5
that sure is a pretty shielding job Sumgai ...
guitars are beautiful creatures arent they ?
|
|
|
Post by JFrankParnell on Jun 17, 2010 17:03:54 GMT -5
I did mine roughly with the copper tape and then did 3 coats of conductive paint around all the seams. Does this seem like a good job or not? Well, with the fact that I went outside the pickguard with the paint notwithstanding
|
|
|
Post by newey on Jun 17, 2010 17:18:44 GMT -5
Looks good, JFP- so long as you read your meter across it as detailed above.
I have been using the conductive-adhesive copper tape available from StewMac and elsewhere. Well worth the extra cost IMHO.
|
|
|
Post by chuck on Jun 17, 2010 20:32:04 GMT -5
another fine lookin shielding job
|
|
|
Post by sumgai on Jun 17, 2010 21:51:47 GMT -5
that sure is a pretty shielding job Sumgai ...
guitars are beautiful creatures arent they ? Pretty hard to argue with that! ;D BTW.... Hi, and to the NutzHouse!
|
|
|
Post by sumgai on Jun 17, 2010 22:01:13 GMT -5
I did mine roughly with the copper tape and then did 3 coats of conductive paint around all the seams. Does this seem like a good job or not? It's a matter of degree. To be a bit mean about it, I must say that over my 50+ years of engineering and technicianing, I've never seen any paint being used to connect wires, pots, switches, etc. Could it be that paint, no matter what the claim, still isn't as conductive as solder? But that's just me, acting like a little kid in a pissing contest. newey's right - if the meter reads less than 2Ω from any point to the jack's ground terminal, then I'd call it ready for prime time. (But Holy Jeebuz man, three coats of paint? That's gotta be more expensive, and a helluva lot more effort, than a 4 or 5 minute solder job, doncha think?) sumgai
|
|
|
Post by JFrankParnell on Jun 18, 2010 11:43:05 GMT -5
lol, I'll measure it next time i have it apart. Yes it did take me some time. Well, I got both the tape and the paint from stewmac, i didnt have any experience with either, so I got both. I started putting down the tape and decided I could do a *pretty good* job with it, but that it would be easier to fill in all the gaps with the paint. Three coats is what is reccomended on the can when you are doing paint only. While the paint is expensive, 3 coats on just the seams and gaps took very little paint. Of course, when i measure it we'll see if it was worth it
|
|
|
Post by morecowbell on Jul 13, 2010 12:41:44 GMT -5
When soldering ground wires to pots: Before soldering, I always use a nail to lightly score the back of the pot in a criss-cross pattern to help the solder "grab hold." You don't have to do the whole pot, just the spots you know you'll be soldering ground to. Seems to help, though I don't know if this falls under best practices.
|
|
|
Post by sumgai on Jul 13, 2010 16:45:12 GMT -5
mcb, ...... I don't know if this falls under best practices. It does. The proper term is called "abrading" the surface. Whether you use a nail-point or something else, so long as the surface plating is scored, that's what counts. You don't need to go all the way down to the base material (usually brass), just making sure that all polish and such is knocked away from the soldering area, that's good enough. +1 to you! sumgai
|
|