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Post by unreg on Mar 18, 2020 6:36:26 GMT -5
Hi all š
Some years ago I learned about a way to shield the bottom of guitar pots with some substance that was in our house. I recently made many scratches in the clear shield, while trying to clean that surface, and now the guitar hum is ten times worse. My only question to you is:
Can you help me to know what substance I used to shield the bottom of the pots? I donāt have the siteās bookmark where I had read some really smart helpful luthierās comment about a cheap shielding. (Itās not foil or tape; rather, itās a household liquid that shields the pots due to the liquidās chemicals.)
This forum seemed very knowledge intense so it seems like a good place to ask; thank you for reading,
Matthew
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Post by reTrEaD on Mar 18, 2020 9:26:49 GMT -5
Hi all š Some years ago I learned about a way to shield the bottom of guitar pots with some substance that was in our house. I recently made many scratches in the clear shield, while trying to clean that surface, and now the guitar hum is ten times worse. My only question to you is: Can you help me to know what substance I used to shield the bottom of the pots? I donāt have the siteās bookmark where I had read some really smart helpful luthierās comment about a cheap shielding. (Itās not foil or tape; rather, itās a household liquid that shields the pots due to the liquidās chemicals.) This forum seemed very knowledge intense so it seems like a good place to ask; thank you for reading, Matthew You came to the right place! I've never used such a liquid but if it's clear and magically shields pots to reduce hum, logic dictates it would be named Clear Magic. If you have trouble finding it and have a friend in the Air Force, they might be able to get you some. I reckon they could go to Base Supply and find it on the shelf, right next to the 1000 yard rolls of Flight Line and gallon jugs of Prop Wash. |
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Post by sumgai on Mar 18, 2020 10:51:10 GMT -5
Somebody's calendar needs adjusting, it's still half a month away from April 1st.  |
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Post by newey on Mar 18, 2020 15:51:00 GMT -5
Matthew-
Hello and Welcome to G-Nutz2!
I'll treat your question as a serious one, and if you are putting us on with this (as RT and sumgai both imply), well, then, you can say "Gotcha!"
If you are now getting "ten times" the noise, I suspect your scraping of the pot has either damaged the pot itself, or caused a faulty connection to it, or perhaps you pulled something loose somewhere else.
Whatever noise reduction you may have thought you heard after applying some mystery "Goop" to the bottom of your pots must have been strictly a subjective response of "hearing what you wanted to hear". Even if there were some sort of liquid stuff (there is shielding paint, of course, but it doesn't sound like that's what you're talking about), applying it only to the bottoms of the pots cannot logically have any effect.
The vast majority of the noise in a guitar signal comes from the pickups. It is extremely unlikely that doing anything to shield a pot could affect the noise level, since pots don't contribute to the noise floor in any appreciable way. And, logically, why only the bottoms? Since the resistive track of a pot turns along the side of the pot shell, one might expect that the sides would be the place to apply the "Goop".
In any event, the shell of a pot is metal. If the innards needed shielding (which they don't), then the metal pot shell would do a better job than anything you might apply topically.
But, again, there is no need or reason to shield pots and any internet advice to the contrary is worth what you paid for it.
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Post by unreg on Mar 18, 2020 20:49:46 GMT -5
Thank you newey! š
I was being honest, but it seems I must have been wrong.
By ābottom of the potsā I was meaning all of the hidden pot area inside the guitar... but, now it makes sense that the pot is entirely inside the guitar and the dial is on top.
I donāt believe I damaged the pots; there are slight tiny scratches; hope the pots arenāt damaged; anyways, the wire to ground the bridge is ordered and so that will help lots, from what Iāve read.
Note: The noise reduction allowed me to record a song... so, unless the song sounds extremely clear thanks to DBX NR, the sound change wasnāt just in my head.
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Post by newey on Mar 19, 2020 12:46:53 GMT -5
It's tough to isolate all the possible variables that may have been involved in the reduced noise. You opened the guitar, you moved things around, you screwed it back together . . .who knows? Plus, there can be differences in the electrical noise environment- fan motor on versus off, fluourescent lamps on versus off.
The reason that all 3 of us who have responded are (to say the least) extremely skeptical about this is that electricity is pretty well understood- it's been a long time since ol' Ben and his kite in the thunderstorm. Absent some plausible hypothesis, based on what we know about electromagnetism, that could provide a mechanism by which a vol. or tone pot is generating noise into the guitar signal, we're not buying into it.
This, of course, assumes a properly made and functioning pot. But even if the pot had its own issues internally and was generating some noise, there still would be no explanation for how a coating over the pot's shell would improve that in any way.
One thought that does occur to me is that, if the material you used were conductive, and if the back(s) of the pot(s) was/were where the grounds were collected and soldered, and if the ground connection to the back of one or more pots were not well-connected, then it is remotely possible that applying the goop "fixed" that bad grounding point and reduced the noise. But even if that were the case, that would not be "shielding the pot",it would be fixing a bad connection, same as if you hit it with your soldering iron to remelt that connection. And, as my dear departed mother would have said "if dog, if rabbit . . .". (IOW, that's a lot of "ifs", so at some point we'd need to apply Occam's Razor).
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Post by unreg on Mar 19, 2020 14:57:21 GMT -5
newey, thank you for all of your helpful words! š
You have a point... maybe I should go and remelt all of the solder. And, yes, almost everything is soldered to the bottom of the pots... there are a few wires, some green square/rectangle with 2 wires, (and 2 resistors I added) soldered to the potsā loops-connections, whatever they are called. Checked all the wires with a multimeter and the wires are all unbroken... but a solder connection may be incomplete; thank you. š
And, I thought maybe I had placed the SM57 microphone too close to the amp; it was really close; maybe that had something to do with the noise too?
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Post by sumgai on Mar 19, 2020 16:03:04 GMT -5
...... The reason that all 3 of us who have responded are (to say the least) extremely skeptical about this is that electricity is pretty well understood- it's been a long time since ol' Ben and his kite in the thunderstorm. Absent some plausible hypothesis, based on what we know about electromagnetism, that could provide a mechanism by which a vol. or tone pot is generating noise into the guitar signal, we're not buying into it. No, the reason is that neither reTrEaD nor I stopped to consider the possibility that the poster might not be using what we like to think of as "the correct vocabulary". The mis-termed "back of the pot" in place of the "under the pickguard" tripped us up completely... or at least it did for me. unreg , I do apologize for my error in misunderstanding you and your intent. Don't worry, we won't put you in the Penalty Box for using incorrect terms, people do that all the time on this Forum.  As newey would say in his version of Real Life Ā®: "Mea Culpa". My only thought at the moment, unhelpful as it might be, is what possible "household liquid" could be seconded to serve as a shield against hum? I know you can't think of it, but neither can I. A paint containing metallic chips, thickly populated enough to actually do some good, is not what I'd call "household", so that shouldn't come to the fore. And equally true, several scratches in a paint-like coating should not increase hum to an unbearable level... another reason to think it's not paint. But no matter what liquid was sprayed on, it's not easy to envision that a complete envelope was merely scratched in a small amount of the total surface area, and suddenly the whole thing becomes worthless. Therefore, I suggest that you follow newey's procedures to check things more thoroughly, and see what happens. HTH sumgai |
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Post by unreg on Mar 20, 2020 8:06:47 GMT -5
Thank you sumgai! š One thought that does occur to me is that, if the material you used were conductive, and if the back(s) of the pot(s) was/were where the grounds were collected and soldered, and if the ground connection to the back of one or more pots were not well-connected, then it is remotely possible that applying the goop "fixed" that bad grounding point and reduced the noise. But even if that were the case, that would not be "shielding the pot",it would be fixing a bad connection, same as if you hit it with your soldering iron to remelt that connection. This thought was genius; thank you newey! š After remelting the solder dots, like you suggested, remembered that I had soldered a wire over a spot on the bottom of the pot that was entirely black... so the solder did not make the connection to the pot. Yes, I wasnāt thinking. The black mark that came with the guitar could have been cleaned away, I bet. Anyways, I remember now that I had explained to a forum that mistake I had made, and that I couldnāt use a soldering iron now bc of my shaking hands due to the large medication amount I was taking for my mental illness. And, one person replied that I should try swabbing rubbing alcohol from the top of the solder down the side of the pot. I donāt remember if I covered the entire pot AND I donāt remember if I swabbed from my Isopropyl Alcohol bottle instead. After researching online about āconductive rubbing alcoholā... some said it was very conductive and others objected... I think a long reply on answers.com helped me to decide to apply the alcohol. And it worked excellently! PRAISE GOD!! š So there is what happened. I think there may be a way to suck up the solder and clean that black mark away. Am I right? Maybe I donāt need to. Havenāt tested the guitar yet. |
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Post by unreg on Mar 20, 2020 10:13:15 GMT -5
My only thought at the moment, unhelpful as it might be, is what possible "household liquid" could be seconded to serve as a shield against hum. sumgai, sorry, my post is mistakenly titled āshieldā, but newey helped me to remember that I wasnāt making a shield against hum; rather I was helping the broken solder make its connection. I donāt think itās possible for me to retitle this thread properly. [ EDIT by sumgai - yes, you can edit the title by editing the first post. I've already done that for you, take a look. ] |
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Post by unreg on Mar 20, 2020 10:59:38 GMT -5
And, one person replied that I should try swabbing rubbing alcohol from the top of the solder down the side of the pot. Honestly, Iām unsure if he told me to swab the liquid down the potās side. But, the rubbing alcohol OR isopropyl alcohol did make that broken solder connected. šš The spot covered with black was the only place that the short wire could be soldered to. The wire was short bc I didnāt correctly plan ahead; though short wires are recommended. Was my first soldering experience. The guitar maker used a lot of solder in that location so the only available spot, with the black mark, was at the potās edge. My soldering iron will not melt the the solder that came with my guitar. Iām using Light-Duty Rosin-Core solder. |
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Post by newey on Mar 20, 2020 11:39:53 GMT -5
As I said, electrical environment . . .
We often get "how do I quiet this particular noise" questions, and the predicate to the discussion is always "did you try it with a different amp? Did you plug the amp into an outlet that's on a different circuit? Did you try swapping cords, eliminating pedal board?" I could go on, you get the idea.
We have debated shielding of different parts/areas for years around here, and I think the consensus is that shielding the pickup cavities with metal foil, done properly, is beneficial to noise reduction with SC pickups. Shielding the control cavity, probably not so much, there's not much wire or parts in there to be picking up noise- but if one is already inside the thing shielding the pickup cavity, and one has the foil already in one's hand, might as well go ahead and do the control cavity as well, can't hurt.
The original G-Nutz "1" site suggested a shielded cable to the output jack, and I sometimes do so. I do not attempt to shield the output jack "canoe" area on Strat-type guitars as there's too little room and the cable tip can contact the shielding.
But if you're truly worried about shielding the pots individually, just shield the entire control cavity and be done with it.
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Post by unreg on Mar 20, 2020 15:16:54 GMT -5
As I said, electrical environment . . . We often get "how do I quiet this particular noise" questions, and the predicate to the discussion is always "did you try it with a different amp? Did you plug the amp into an outlet that's on a different circuit? Did you try swapping cords, eliminating pedal board?" I could go on, you get the idea. We have debated shielding of different parts/areas for years around here, and I think the consensus is that shielding the pickup cavities with metal foil, done properly, is beneficial to noise reduction with SC pickups. Shielding the control cavity, probably not so much, there's not much wire or parts in there to be picking up noise- but if one is already inside the thing shielding the pickup cavity, and one has the foil already in one's hand, might as well go ahead and do the control cavity as well, can't hurt. The original G-Nutz "1" site suggested a shielded cable to the output jack, and I sometimes do so. I do not attempt to shield the output jack "canoe" area on Strat-type guitars as there's too little room and the cable tip can contact the shielding. But if you're truly worried about shielding the pots individually, just shield the entire control cavity and be done with it. hmmm... I guess you didnāt read any of my response posts? |
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Post by sumgai on Mar 20, 2020 16:26:56 GMT -5
unreg, Those black dots are evidence of "flux", a chemical usually included within the solder itself. But yes, it can be purchased separately, and in fact several of your fellow Nutz do exactly that. Flux is used primarily to clean the area, thus enhancing the adhesive properties of solder. When it is not thoroughly heated, a black and/or brown residue remains. And as you figured out, that residue interferes with a good solder connection. We call this a "cold solder joint" because it usually takes no more than a gentle re-heating of the joint to make everything copacetic. Hopefully all is good now, yes?  HTH sumgai |
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Post by unreg on Mar 21, 2020 11:39:37 GMT -5
unreg, Those black dots are evidence of "flux", a chemical usually included within the solder itself. But yes, it can be purchased separately, and in fact several of your fellow Nutz do exactly that. Flux is used primarily to clean the area, thus enhancing the adhesive properties of solder. When it is not thoroughly heated, a black and/or brown residue remains. And as you figured out, that residue interferes with a good solder connection. We call this a "cold solder joint" because it usually takes no more than a gentle re-heating of the joint to make everything copacetic. Hopefully all is good now, yes? HTH sumgai Thank you sumgai! š I found that Iām supposed to use an iron to heat the cold solder joint? (An iron wonāt fit in the cavity where the pots are); but, now that Iām thinking about it, the cold solder joint fixing info came from a page with lots of circuit board images; irons fit circuit boards. š The massive 10x hum increase is gone now, but there is still a small hum; so maybe the heat from my soldering iron fixed that cold solder joint? I donāt know bc I never purchased a solder sucker to remove that solder-with-black-flux-specks so I would be able to clean the flux spot away. Maybe the small hum will be eliminated after my wire arrives and so then the bridge will be grounded. š edit: ooh, my guitar uses two humbuckers; so the single coil hum problem is mute |
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Post by reTrEaD on Mar 21, 2020 12:05:51 GMT -5
I found that Iām supposed to use an iron to heat the cold solder joint? (An iron wonāt fit in the cavity where the pots are); Just use the pointy end. |
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Post by unreg on Mar 21, 2020 20:32:53 GMT -5
I found that Iām supposed to use an iron to heat the cold solder joint? (An iron wonāt fit in the cavity where the pots are); Just use the pointy end. Is the pointy tip of a large iron parallel effect-wise to the tip of a soldering iron? edit: Iām confused... was that another joke? By āironā they meant āsoldering ironā? |
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Post by sumgai on Mar 22, 2020 11:30:04 GMT -5
unreg, Yes, it was a joke. reTrEaD is known for his slightly warped sense of humor, so don't worry over it.  I don't know what wattage your current soldering iron has, but most low-power units can heat up the back of a pot with little or no problem. Many here in The NutzHouse use a 15 or 20 watt iron with no problems. I personally use a 40 iron, because I have lots of different things to do with it. If you are unsure of how much heat your iron can put out (measured in watts used), then I suggest two things, in order of ease and expense: a) Get a new tip; b) Get a new iron. If your iron is old, or you don't know who made it, then getting a new tip might be difficult, I understand. But new soldering irons can be pretty inexpensive if you shop around. For anything you're going to do inside of a guitar (or effects pedals too!), you can get by with a 20 or 25 watt iron just fine. But along with that, you want to use good solder, not some nasty old stuff that's been in the back of the parts bin for 20 years or more - which may work, or it may not, who knows. Best to buy a fresh roll and be sure that it'll work properly. Tips on re-heating a solder joint: - As with a new joint, tin the tip first. Just dab on a tiny bit of solder before you apply the tip to the components/wires. - Try to get the iron's tip to touch both/all parts at the same time. Often this isn't easy, or practical, so touch the largest surface first. That translates to, a spot on the back of a pot should be started to heat up, before touching the iron to the wire(s). - Again, use a small amount of solder and touch exactly where the iron's tip is touching - you should see a whiff of smoke. - Hold the iron onto the parts until you see either the solder is running freely (and probably spreading out), or until you see that the brown/black stuff is gone. - Let the joint cool, then physically tug at the joint - gently! If it's physically secure, then you can test it electrically in whatever manner way you wish - multimeter, actually playing your guitar, etc. That should do it!  HTH sumgai |
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Post by unreg on Mar 28, 2020 21:36:51 GMT -5
Thank you sumgai!  Your soldering tips help me solder so much! So, after cleaning flux away AND installing a bridge ground wire AND fixing the soldering on the jack... the ground jack wire was barely connected, maybe bc insertion/removal of the guitar cord caused many of the ground wires to become broken?... now the bridge pickup is silent. Perhaps its hot wire became disconnected? (Also, the middle switch position, where both pickups should be heard, is silent.) Any clues? (I added āunreg?!ā to the end of this threadās title to attempt to make it known that this thread will be home to further questions from me. Is that ok? Should I make a new thread?) |
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Post by thetragichero on Mar 28, 2020 22:37:32 GMT -5
sounds like something is shorting to ground
have you tried plugging into an amp (not loud!) before installing in the guitar and lightly tapping the pickups to confirm they're working in all positions. then it's most likely shorting in the shielding.
still not totally working? then there's a short in your wiring
divider and conquer!
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Post by sumgai on Mar 29, 2020 11:29:25 GMT -5
Thank you sumgai! Your soldering tips help me solder so much! So, after cleaning flux away AND installing a bridge ground wire AND fixing the soldering on the jack... the ground jack wire was barely connected, maybe bc insertion/removal of the guitar cord caused many of the ground wires to become broken?... now the bridge pickup is silent. Perhaps its hot wire became disconnected? (Also, the middle switch position, where both pickups should be heard, is silent.) As thetragichero said, you have a short somewhere, either in the wiring, or from the wiring to the shield. If the Bridge pup's hot wire were open (disconnected to anything), then Position 2 (both pickups combined) would sound out with only the Neck, as if it were in Position 1. Actually, that's not our preferred method. We'd rather keep each thread "on topic", because readers who want an answer can search quickly, and not have to wade through a lot of non-germane material. Yes, please do so. But you can use "unreg?" in each title, if you so desire. HTH sumgai |
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Post by unreg on Mar 29, 2020 22:45:42 GMT -5
sumgai, I understand now, thank you. This reply has to do with hum troubleshooting so a new thread wonāt be made now. thetragichero, thank you so much! Started testing each ground wire with a multimeter and all electronics are grounded. Then I noticed a dark (black) mark on the top of the cavity containing the volume, tone, and switch. This black is on top of dark green paint so itās kind of hidden. Anyways, multimeter testing made evident that a current can travel through the surface of that black mark. That black must be the shielding? The black continues over the side of the cavity and it turns out that the entire cavity has been painted with the black. So, It must be a short in the ground to my shielding bc I tapped on each pickup in each switch position and could hear all the tapping through my amp. Then the pickups started working in every switch position... but, there is a bit of hum. I remember removing a solid piece of something that was stuck between the cavity wall and my volume pot while removing flux and cleaning. Sadly, that solid piece was tossed away. Now, I am thinking that solid piece made the ground connection for my shielding. (Do you think that missing shielding ground causes a small hum?) After watching yt, it seems that I could screw a ground wire into the black wall shielding. Does anyone know what that solid piece I threw away was? If so, do you recommend replacing that solid piece or screwing a ground wire into the black wall? Any tips? Iām lost. edit: this ādark (black) markā is not flux |
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Post by thetragichero on Mar 29, 2020 23:03:37 GMT -5
it's quite possible your shielding is already grounded through one or more of the pots (if there are any ground wires connected to the back of a pot, the pot is in contact with the shielding). it's also possible, depending on where the output jack is, that it is connecting the shielding to ground
is the hum coming from the guitar or from the amp? it's possible you could be chasing your tail when the hum is coming from elsewhere
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Post by unreg on Mar 29, 2020 23:17:00 GMT -5
thetragichero, thank you again for sharing your knowledge! I believe the hum is coming from the guitar... it seems that when the cable is unplugged from the amp, the amp is silent. Will check that tomorrow when others arenāt sleeping. |
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Post by thetragichero on Mar 30, 2020 9:33:10 GMT -5
most amps have a shorting jack on the input ask that could be keeping it silent
we're talking about low frequency hum or high frequency buzz?
there are some high frequency sounds (lighting, pretty much everything on my recording computer, cellphone activity) that i don't think you'll ever be able to block out
i learned not to leave my phone on top of my amp or on in my pocket by hearing noise in my signal
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Post by unreg on Mar 30, 2020 18:57:21 GMT -5
When the guitar cable is plugged in there is a very quiet hum (low frequency?) now. This is tons better than it was!
Hmm... there isnāt any lighting other than a regular lamp, uses a simple light bulb, plugged into the other outlet on the wall outlet... and Iāve removed everything on top of the amp. There is a dresser on one side and my bed on the other. The bed has a metal bar thatās around an inch from the amp. Behind the amp sits the power strip; the amp plugs into a Hum-X and the Hum-X plugs into the power strip.
When the amp is turned up for 4track recording, the quiet hum grows.
edit: the power strip is empty otherwise.
final edit: I seem to remember that solid piece was removed by me before and a giant hum appeared; then after reinserting that solid piece between the black wall and the volume pot, the hum went away. As you know, I no longer have that solid piece.
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Post by thetragichero on Mar 30, 2020 21:26:54 GMT -5
can you check continuity between the volume pot and ground?
can you describe this "solid piece"?
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Post by unreg on Mar 31, 2020 0:27:24 GMT -5
can you check continuity between the volume pot and ground? can you describe this "solid piece"? An analogue multimeter was used with a pole piece on the volume pot and the other pole piece on the outside of the jack AND it gave a perfect 0 reading when checking resistance. Does that equal continuity? Iām sorry for failing to use the correct terms. To describe the āsolid pieceā, this image might help:  The green v (for volume pot) points to about where the āsolid pieceā was. After tossing it into the metal trashcan, it made a definite thud sound. Maybe it wasnāt metal; it may have been painted with the black stuff that allows currents. Notice I also circled the black mark on top of the cavity that contains the volume tone and switch.  ^there is a side view of the cavity. Notice how the black current āpaintā doesnāt fill the entire wall; could that be the problem? |
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Post by thetragichero on Mar 31, 2020 0:50:46 GMT -5
have continuity between the black painted cavity and the volume pot? if not a piece of wire connected to the volume pot and to the cavity (solder the other end to a washer or something and screwing that down into the cavity)
take the reading first though
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Post by unreg on Apr 1, 2020 0:33:29 GMT -5
Got a digital multimeter today... and it measures continuity. So, yes, there is continuity between the volume pot and the jack-ground-part. A beep sounds so itās less than 50 ohms. The continuity of the black paint ranges anywhere from 160 ohms to 500+ ohms... sometimes the meter doesnāt show a value. The meter RARELY shows a continuity value when probing the volume pot and the black paint.
When switching to resistance the values show all the time... I bet the Klein MM600 can switch out of auto mode, and so it could frequently show continuity values, but I havenāt figured that out yet, sorry.
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As newey would say in his version of Real LifeĀ®: "Mea Culpa".
Your soldering tips help me solder so much!
