Shielding without re-grounding?

[BlackAngusYoung]

Hello, I'm new to the forum and to working on my guitar. (Pretty new to any kind of electronics work, actually.)

I've had my Squier Mini Strat for a few years and always suspected it sucked. It's the only electric guitar I've ever tried and I always found it really annoying, like it was making a bunch of noise that had nothing to do with me and I'd have to be extra skilled to turn that into music. I bought it out of haste so I could practise guitar with headphones and not bother my roommate's evil girlfriend with my acoustic. So when I found it unimpressive I wasn't too surprised, as I was already pretty sure I'd prefer the acoustic. But then recently I found reviews about this guitar in which people who know what they're talking about (at least more than I do) confirmed everything I thought might be off about it. The biggest thing was that it needs to be shielded, which I have never heard of before.

The buzz on 1,3 and 5 is pretty annoying (especially with headphones, which is what I wanted it for) and definitely worse if I hold it near a fluorescent light bulb. So I shielded it using the aluminum tape method and the results are... the same! I do have a pretty good guess why: I skipped all the parts that required soldering except to disconnect and reconnect the wire to the jack in order to pull it through the body to work on everything. I probably misunderstood something, but I got the impression the rewiring was only important for people who are going to play with different or older equipment they're not too sure about the electrical integrity of. I'm probably only going to play it at home with my modern amp I got at the same time, which is probably pretty harmless since it actually runs on batteries (Roland Micro Cube that totally kicks and seems to be the perfect companion to the Mini Strat.)

I'm pretty sure I did a good job on the aluminum tape part and my continuity tester thinks so too. So what I'd like to know is if the remaining buzz is most likely from the steps I skipped or should I notice a difference with just the aluminum shielding and have therefore done something else wrong?

I should probably mention that I haven't actually restrung it, just plugged it in to see if the buzz is still there and it is. I doubt it has anything to do with whether it has strings on it, but figured I should mention that in case anyone thinks it might.

I'm sorry if this is a stupid question or something that's been covered already in the forum or on the main site. There's so much information and I want to learn it all but I'm trying to take it in all at once and it's a bit overwhelming (but that's great, of course!!!)

I'd really appreciate it if someone could give me a very simple answer as to what I absolutely need to do in order to get rid of the buzz.

And as far as the wiring schematics are concerned, is there anything available anywhere that would be closer to what I'm actually dealing with than the standard Stratocaster drawings usually provided? I think it's pretty close to the standard setup except it has a fixed bridge without tremolo (the strings don't go through the body of the guitar) and there is only one tone control as well as the volume, not two.

Thanks very much for any help.
Looking forward to a time I'll know enough to help others, too!

[JohnH]

hi b a y - and welcome to GN2.

The essential parts of shielding are:

foil under the pickguard
foil in the cavity
all parts are electrically connected to all other parts, so the pickguard foil touches the edges of the cavity foil, usually the cavity foil is lapped a little over the sides of the body so the two foils get pressed into contact when you screw down the guard
the foil is connected to ground

That last bit is the key, that maybe you dont have, which activates the shielding. It doesn't matter much in theory, how you make that connection. If you have the foil under the pickguard, then it will be in contact with the potentiometer bodies, which are grounded themselves, so it should just happen naturally

You dont need to rewire necessarily.

But the other thing is, in position 1, 3 and 5, you are using one single coil pickup, which will always pick up hum. This is particularly noticeable if you like a lot of gain. It's just the way it is with a Strat and you can use positions 2 and 4 which are noice caneclling. Shouldn't be too bad though.

John

[BlackAngusYoung]

Ok. Thanks for your prompt reply!
I hope it's not accidentally connected to anything wrong (I don't think it is) but if connecting to the ground through the pots like you described is good enough, there's definitely no worry there. Also no worry when it come to the part about the pickguard shield touching the cavity shield. I even traced parts of the pickguard on the tape so I could stick the exact right shape on the guitar body. But I guess what I might not understand is whether the cavity tape only needs to make contact somewhere or should it be lipped up all around the cavity? Now there are spots where the tape only goes on the cavity walls so I'll make sure it goes over the edge all the way around. I just thought I'd better ask if I've done well so far before going through the trouble of putting the strings back on.

Right now, I can use my continuity tester to see that there is continuity between everything metal on the guitar. Is that a good thing, then? All screws, knobs, around the output jack, and the bridge. Really, everything metal except the tuners (but there's no strings yet,) the strap buttons (but that's just silly,) the magnets, and the part in the jack which I know shouldn't be grounded.

[newey]

BAY-

But I guess what I might not understand is whether the cavity tape only needs to make contact somewhere or should it be lipped up all around the cavity?

As long as contact is made so as to be sure the shielding under the pickguard is in continuity with the cavity shielding it should be ok. I usually make sure that the cavity shielding and pickguard shielding come into contact at at least 3 of the screw holes so that, once the guard is screwed down, I know at least one or two of those spots are making good contact.

A good shielding job should help somewhat, but your particular noise issues may be exacerbated by the use of headphones. You also mention florescent lights as worsening it, as they are known to do. Have you tried using your guitar without the headphones? Is the noise still at an objectionable level? Have you tried the amp, with and without headphones, in a different setting without florescent lights, etc., around? Is it still too noisy?

Alternatively, trying a known quiet guitar (HB style) through your amp/headphones may shed some light.

[ashcatlt]

Welcome a'board.

To answer your last question first, yes that's good. There are a few pieces of metal aside from what you mentioned which should not connect to ground. You know, like some of the lugs on the switches and pots.

The more "air tight" the shield the better. The pickguard and cavity foil need to both find ground without much resistance. Overlapping out of the cavity is a good way to accomplish this. It doesn't necessarilly have to contact all the way around. We might expect it to work a bit better if it did, though. Not sure how big that bit is, though.

My mini-strat was about half shielded when I got it. I just got mine a couple months ago, yours might be older, but mine's got conductive paint covering the cavity. All I had to do was foil the pickguard. There was even a convenient ring connector screwed into the cavity with a wire connected to ground, which accomplished the same thing as your overlapping foil.

I have to say I didnt' ever test the thing before I shielded it. I knew I was going to re-wire it, so why mess around. I don't have an inordinate amount of noise from it now, though it appears to be microphonic. Do you have an amp you can plug into with a little gain to tell me if it makes a horrible high pitched squealing when you get the pickups close to the speaker?

Noise in any audio system is for me the most frustrating thing to try to troubleshoot. There are so many different factors. You'll never get rid of all of it. Most of the time when people complain about noise it's either because they've got a skewed perspective (expecting silence) or it's really bad. I think you're the latter, but you might try a second opinion.

Better yet, try a second guitar! Are you sure it's the mini's fault?

Then I also want to know, what happens to the noise when you physically touch one of this miriad of parts which connect to ground with bare skin?

[newey]

And as far as the wiring schematics are concerned, is there anything available anywhere that would be closer to what I'm actually dealing with than the standard Stratocaster drawings usually provided?

I checked Squier's website, they have a pdf of the mini-Strat wiring. Unfortunately, while they picture the mini-Strat with 2 pots, the wiring diagram for it shows 3, in a std Strat configuration with 2 tones. Not much help I'm afraid.

The diagram does, however, show a ring connector to the cavity, as Ash suggests his has. Your new shielding should be grounded through that lug, assuming you reconnected it after your shielding job. If you didn't, you should do so, it's a little extra insurance to be certain your shielding is well grounded.

While everything should, in theory, be connected via the shielding touching the shells of the pots, which are in turn grounded, I never like to rely only on the pot shells making good contact with the aluminum foil on the back of the pickguard. It's easy to scrape up the foil while installing the pots if they move while you're tightening the hexnut, and I don't trust the resulting connection. You did indicate you have continuity throughout, so presumably that connection was good enough in your case.

[ChrisK]

OK, so you've shielded the wiring cavity where wires have few turns afoot.

Did you shield the pickup cavities where inductors, each with about a mile of really fine wire that is tightly wound into an antenna loiter?

The pickups pickup much of the noise (that mile of wire thing). Shield each pickup cavity in the body and run a connected wire from each back to the star ground in the wiring cavity.

If it wasn't the single coils being the culprit, the humbucker would never have been invented.


You mention that you have conductivity between the parts of the shield. Do you have conductivity (less than a few Ohms) between every part of the shielding?


This might help, it's for a Strat Jr. The pickup selector might be different, but the general layout will be similar.
www.fender.com/support/diagrams/pdf_temp1/stratocaster/0133800A/SD0133800APg2.pdf

[ashcatlt]

The mini strat only really has one big cavity.

I looked at the switch I pulled out of mine. I cut the wires off real short, so it's kind of hard to tell what was going on. It's really just standard strat wiring except you'd ignore the side of the switch which does that half-assed tone knob assignment. Mine has a wire to one of the lugs on that side which runs to the back of the volume pot. Not sure if there was anything else on the other lugs. They all have solder on them, but don't look like there were wires.

If you could take a digital photo we could sort it out pretty quick.

[BlackAngusYoung]

Ashcatlt, I have many (MANY!) digital pictures of everything from every angle. lol. I would have offered one but I honestly didn't expect so many people to want to help sort it out for me. So thanks everyone!!!

Thanks ChrisK a lot for that schematic. I had only ever found the other one mentioned, which says it's for the Mini but doesn't really seem to be.

My Mini is about 5 years old. It doesn't have the grounding ring or shielding paint mentioned by Ashcatlt. The only shielding it came with was a little stylized triangle shape of aluminum foil on the pickguard where the controls are mounted. From that group of controls, the foil extends no more than a quarter inch in every direction. Pretty lame but I guess they're trying to do it better now, so that's good. The insides appear to have the same finish as the guitar body but very badly done with sharp blobs pointing up all over place poking holes through my aluminum tape.

After writing back after the first reply from JohnH, I opened it up to make sure everything looked taped well and I think it did. I added a bit more for one of those "air-tight"ish seals, but OCD runs in my family so I had it covered pretty well the first time. Then I taped the cavity under the output jack, even though I'm pretty sure I read somewhere that that shouldn't be necessary. (I put non-conductive tape on the back of the part that shouldn't be grounded just in case a piece of aluminum became unstuck and touched it.)

I don't know if I originally just panicked, or if I'm one of those people who expected complete silence, or if shielding the jack area was the key.... but the end result is impressive! The buzz on 1,3 and 5 is hardly noticeable now, unless I hold it within 2' of the light or really close to the amp. It's especially hard to hear any when turning the amp up to get more volume and keeping the guitar's volume down low, which didn't really seem to make a difference before.

Yes, newey, I always knew the buzz was worse because of using headphones and I still have that headphone buzz but it's definitely a big difference. I can deal with that (even just flicking the wire behind my back away from the guitar helps) because I'm used to that kind of buzz from even just walking through the mall wearing headphones and passing stores with neon window signs. (Ever walk through one of those anti-theft sensors wearing headphones? It's so frightening.) It was the combination of both hums and how clearly they're heard with headphones that was really driving me crazy. Well, driving me away from the guitar really.

But all is well now. Thanks again!

[mr_sooty]

Dec 7, 2008 12:42:35 GMT -5 ashcatlt said:

My mini-strat was about half shielded when I got it. I just got mine a couple months ago, yours might be older, but mine's got conductive paint covering the cavity. All I had to do was foil the pickguard. There was even a convenient ring connector screwed into the cavity with a wire connected to ground, which accomplished the same thing as your overlapping foil.

This sounds similar to my 08 American Standard, which had sheilding paint and a jug screwed into the cavity. But the sheilding paint didn't overlap the top of the guitar, so wasn't making contact with the foil. Are you saying this isn't necessary because of the lug? That seems odd because all the instructions here have both the lug and the overlap.

I actually put conductive tape all over the top of the conductive paint and overlapped the edge. It was good, but in some venues I still had some noise issues. So I got some Dimarzion Area 58/61 pickups, and combining them with the sheilding, I now have the quietest strat in history (well.....).