The Squier Project – Part 3 – Do something!

Ok, so now onto the actual work. First, we need some materials. The plan is that we’re going to shield the cavities of the body. There are a number of commercial vendors that sell foil tape and shielding paint for this, as well as braided wire shielding. These products will do exactly what we’re looking to do, although there are limitations. The idea is that we want to make certain that whatever it is we use to shield the body of our Squier project is well grounded. Remember from the earlier articles, that is the most important aspect of our project. If it’s not well grounded, it’s not going to help. In addition to being difficult to ground effectively, the foil tape can be difficult to work with.

So, being the inventive sole I am, and after thinking about what I already had on hand to work with, I chose an alternative. About a year ago I had to repair the flat roof on my bay window, and needed some flashing to go between the roof and the house. The original had been copper, and I wanted to retain that look, so I had purchased a roll of copper flashing from Home Depot, manufactured by a company called Sandell. It wasn’t cheap by any means, but was something I already had, so it would fit the bill. The only issue was that one side was coated with a black tar-like material. I figured that if I could find a solvent that would remove it, then it would be just the right thickness for what I wanted to do. From working with it prior, I knew it wasn’t so flimsy that I would burn through it when soldering (important in our project), and not having a tape backing, wouldn’t be prone to sticking where I didn’t want it. Additionally, the adhesive backing would be likely to burn while soldering, although not having tried it, I can’t say for sure. Perhaps you can find a roofer that would give you a scrap piece for free, maybe even without the tar adhesive!

So, I had my copper shielding foil. I started the project by removing the tar adhesive from the copper. I found that I could simply apply some mineral spirits (liberally), and use an old toothbrush and the adhesive would just melt off. Here’s a picture of a finished piece:

Copper foil after cleaning

So that done, I now needed something to stick the foil to the cavities. I didn’t want to go with adhesive tape due to the soldering I was planning on doing. I had thought of spray adhesive and contact cement, but I was again concerned about things sticking to places I didn’t want it sticking to. Basically, I wanted a few minutes to arrange my foil before it stuck into place, and figured that removing and re-applying it to adhesive tape was going to be a problem, and I know that contact adhesive doesn’t offer you that option. So, I opted for two-part, five-minute epoxy. Two-part epoxy is generally very heat tolerant, so I had that covered. And five-minute epoxy gives me 5 minutes to finalize the placement, which should be plenty of time. Additionally, it can be easily drilled and will fill any minor imperfections in the cavities. So, I should get an impressive bond, and still be able to work with it for a few minutes. Here’s the epoxy I chose, purchased at Home Depot (it’s very near my house):

Loctite Epoxy

So, here’s the list of the other things I used in this project:

  • Tools – soldering iron, screwdrivers, drill, drill bits, X-acto knife, wire strippers, etc.
  • homemade fixture to hold the guitar – I’d already made this (see below)
  • Electronics solder – I had this already
  • Hookup wire – assorted colors
  • solder lug – actually, a stak-on lug, but I used it as a solder lug
  • A screw, flat washer and lock washer

I think that’s it. I already had all of this stuff. I used to be an engineer, and also had my own equipment repair business, so I’ve collected all sorts of tools and materials over the years. The fixture that I mention above to hold the guitar I’d built not long ago. It’s simply a 2×3 with one side cut at an angle, and then I shaved out a C-shaped notch in the middle to hold the neck of the guitar. Then I took a 3/4 x 3/4 piece of wood, and rabbited it into the 2×4 at a right angle, and then attached another 3/4 x 1/2 piece at a right angle to that, creating an “H” shape. The body would sit on the 3/4 inch stock, with the neck resting in the notch on the 2×3. During this project, I put masking tape over the fixture, as it would be sitting on this for longer than typical and I didn’t want it making marks in the guitar finish.

So, first thing to do is mask off the body to prevent accidents with either dropped tools, solder, or epoxy. We want to keep the finish in as good a shape as when we started. I used heavy newsprint (the page that they use to hold the weekend advertisements) to cover the guitar, held in place by plain masking tape (I used the blue kind you get in the paint department). Here’s a photo of the guitar all masked off:

Body is all masked

You’ll notice the trimmed-up foil there as well. I started to trim a piece of foil that will fit into the cavity base. This will cover the bottom of the pickup cavities. Given it was the first piece, it turned out to be the worst of them all. As the project progressed, I learned some technique that made things better, so you’ll see that later pieces look much neater.

I used ordinary scissors to trim all of the foil. It’s just the right thickness so that you can  use scissors to cut it, and still not have it flopping around while you’re doing that. What I did was to place the cleaned foil over the cavities, put a couple of small pieces of masking tape on the edge just to hold it in place, and then run my finger around the edges of the cavities. Done correctly, this will leave an impression in the foil in the shape of the cavities. Don’t press too hard (my mistake), as it will create extra material around the edge which will then interfere with your test fit into the cavities. I did this, and initially had some issues getting the proper fit. Also, check the cavities for different depths as well. Mine was slightly raised between each pickup cavity, which meant that the distance between cavities was actually slightly longer than the actual outline of the cavities provided – it ends up being the distance plus 2 times the depth difference. This meant I was really lucky with that extra material! Once I got it down to the bottom of the cavities, and was able to spread it out enough to make up the difference in depth. Whew!.

So, after getting my first piece of foil test fit to my satisfaction, I mixed up a batch of epoxy and set to work. I have to admit, I was a bit nervous about how it would go, but I had done as much preparation as possible, so it wasn’t going to get any more likely to turn out well than now. I squirted out a silver-dollar sized blob of each part of epoxy and set about mixing furiously. I only had 5 minutes or so, and I had no idea how long it would take to do this. After the epoxy was thoroughly mixed, I used a cut piece of a paint stick (3/8″ wide strip of wood) to apply it to the bottom of the pickup cavities. I worked quickly, and covered the entire base of the pickup cavities, being careful not to get any on the sides of the cavities. Once completed, I slowly pushed the foil evenly into the cavity, and worked it into the epoxy. Here’s the result of that first bit of foil:

Shielding first pass

I learned a few things from that first pass. First, the amount of epoxy I mixed up was nearly twice what I needed, so I can mix much less next time. Second, I applied way more than I needed, and because of that it tended to run out onto the top of the foil in places. Lastly, I should spend a bit more time test fitting the foil, and should do a better job of smoothing it out. Having a better test fit means less of struggle getting it into the cavities without messing up the epoxy. Smoothing out the foil will just make it look nicer.

So, let’s finish up the rest of the guitar. I’ll pre-cut and test fit the rest of the foil, and then epoxy it into place. Next up is the controls cavity. I decided for this pass that I would try to include some of the sides, as that would mean less soldering. Here is the controls cavity in the test-fit stage:

Controls test fit, with some soldering.

As you can see, I also did a bit of soldering. This can be much simpler to do before it’s glued into place, as once it’s glued down, the epoxy will act as a heat-sink, causing the soldering to take longer. Additionally, if some of the epoxy leaks through, you’ll need to burn that off before the solder will adhere. So, after getting it all and fitted to the cavity, I decide that I want to enlarge the holes drilled from/to the controls so that I have more room to work with. So, being careful not to scrape through the tape and finish with the drill, I enlarged the holes:

Enlarged pass-thru hole

Ok, while I have the drill out, and before I finish with the foil, I want to try something with the tremolo bridge. You’ll remember from my last post that I mention that often with these single-coil guitars that if you rest your hand on the bridge that it will get quieter. To me, this means that the bridge is not grounded as well as it should be. As such, I did a bit of thinking about how it’s actually grounded. In all the cases I’ve seen, the bridge isn’t grounded directly, but rather the spring retainer for the tremolo springs is grounded. That is the case for this strat, in that a ground wire is soldered to the spring retainer, and that wire passes back though a hole in the body to the controls cavity where it is then soldered to the back of the volume pot. This means that the ground for the bridge is from the spring retainer, through the springs, then to the bridge (and the strings). The issue with that is the springs and everything after that. Have a look at this drawing of an air-core inductor:

air core inductor

Looks like a spring, doesn’t it? That means that when your tremolo springs are under tension (meaning spaces between the coils), it’s acting as an inductor. As such, when exposed to an AC signal, you should end up with a differential at the bridge due to the spring’s impedance. That means your ground is only a DC ground, and that the bridge’s ability to maintain an AC ground is limited by the inductance value of the spring (you can do the math yourself if you like, or you can just trust the theory ;-). The issue here is that you’ve now electrically isolated both your bridge and your strings from a solid ground.

What I decided to do was to attempt to get a more effective ground at the bridge itself. After thinking about it, I felt there were two options: Run my copper out of the bridge cavity and up under the edge of the bridge where it mounts to the body, or ground one or more of the screws by drilling an intersecting hole from the bridge cavity to to the screw hole. I chose the latter, mostly for aesthetic reasons, although there was the thought that the copper under the bridge would be prone to wear, and potentially to maladjustment of the bridge itself. Here’s a shot of the process of drilling the holes:

Grounding the bridge

As you can see, I put a small Allen wrench into the screw hole, and then I drilled from the cavity until I hit the Allen wrench. This was so that I didn’t drill too deep, as well as to let me know that I’d actually penetrated the screw hole. If I were to do it again, I think I’d have then removed the Allen wrench and drilled just a bit more to ensure there wasn’t any remaining wood blocking the hole, but c’est la vie.

Ok, so that’s it for modifications to the interior, now to finish the shielding. Here’s my pre-cut, pre-fit pieces of foil:

Some foil for the controls cavity

Foil prepped for the pickup cavity sides

As you can see, I’ve both formed the foil for the cavity sides, as well as forming the base edge where it will meet and be soldered to the cavity bottom. You’ll note that I’ve clipped out the corners of the bottom lip so that when I fold in the sides to make the base edge it doesn’t get all bunched up. Additionally, on the curved edges of the middle cavity and controls cavity, I’ve clipped out small V-shaped pieces at intervals to ensure the same ripple-free edge on the bottom. This allows me to create a nice flat base.

Ok, that all done, we epoxy it into place. Same deal as before, mix up the epoxy, spread it very carefully this time, being sure to not drip it on the bottom of the cavities. Then, carefully applying the foil into place and smoothing it all down. When it’s all in place, you can take a rag (not a paper towel), and wipe up any excess or mistakes you’ve made. The bottle says you can use acetone to clean up any excess, but I think it’s not only unnecessary, but is a very volatile and smelly solvent. A dry rag will do most of what you need to do, and anything else will burn away with the solder. Not apply too much is really the best plan here. You can always practice on a scrap piece of wood or something to ensure you’re using the correct amount.

Ok, so the foil is done! Now we can move on to the soldering. The first thing I want to do is get a good ground to my bridge. I’ve placed the bridge into place, and installed two of the mounting screws into the two holes that I drilled to earlier. Then I take a short length of scrap wire, strip it back about an inch and tin it (melt solder into the wire where the wire is exposed). Then I place the wire all the way into my drilled hole until it contacts the screw holding the bridge and bend it over at the hole edge. Then, applying my soldering iron to the wire and the foil simultaneously, I head the wire and apply solder to it. I keep melting in solder until the solder completely fills the hole and starts to push up above the level of the foil (basically, fill the hole until it overflows). Here’s a picture of the finished product:

Grounding the bridge to the foil

Do that to both of the screws and hopefully we’ll have a good ground for our bridge. When you’re done, you can simply clip off any excess wire and solder the rest to the copper. I tested the ground by measuring from the bridge to  the farthest cavity with an ohmmeter, without the spring retainer or springs installed, and got a solid ground, so I know that I had a decent bridge ground just from the grounding to the screws, which means that the springs will now be grounded on both ends, so no impedance!

Ok, finish up soldering all of the foil together to ensure a good bond to ground, and we’re done! Here’s the final product:

Soldering done!

And although a bit blurry, you can see how I’ve soldered the sides to the base of the cavities:

Sides soldered to base

When you’re soldering the foils together, it takes some patience. Put a decent sized blob of solder on the tip of your iron, then apply it to a starting point on your foil. Let it heat up, slowly apply more solder, while lightly rubbing the iron against the foil. Any epoxy on the foil will slowly burn away, and the flux will help clean the foil, allowing the solder to adhere. You should be able to identify when the solder is actually adhering to the foil, and at that point start working your way along the foil seam. You’ll need to apply more solder to the tip of the iron as you move so that the flux can do it job, and the solder can maintain good contact with the foil so that the heat transfers (the solder is needed so that the heat transfers efficiently to the foil – without it this job would never get done). You should see the solder flow to the foil, almost as paint would. If when you drag your soldering iron along the seam, the solder gets dragged along with the iron, exposing the copper foil, then it’s not really flowing. You’ll need to go back and heat it up while applying more solder. Also, be sure to keep the tip clean by wiping on your damp sponge.

That’s it for this part! Next up, we’ll do a bit of work insulating the copper in places to avoid shorts, and then we’ll start our reassembly.

One Response to “The Squier Project – Part 3 – Do something!”

  1. […] if you’ll remember from our earlier posts that our most important aspect of this project is to make sure that we have a good ground. This […]

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