The Squier Project – Part 4 – Finishing up…

Ok, so the end of the road in sight, let’s finish this puppy up. We now have a our internals all sheilded, we’ll start putting in the electronics and then reassemble everything.

Now 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 will ensure that our work is actually a shield, and not just another antenna. To start off, we need to figure out how we’re going to bond the parts to a common ground point. Fender generally does this by soldering everything to the back of the volume potentiometer. The rumor goes that this in fact sets up what is known as a ground loop. I strongly disagree. If you don’t do a good job soldering and making sure that all grounds have the same potential, then yes, it can create what’s known as coupling. Ground loops are actually something different, but I won’t get into semantics here. Let’s just say that if the wire soldered to the back of the pot and the shielding that you just added both have zero resistance and zero impedance to ground, then there is no possibility of it adding any noise to your guitar. It just can’t. It’s a physical impossibility. If someone can explain to me the mechanism that causes this, I’d be thrilled to know, as apparently my 20+ years of experience has let me down here.

I believe the theory arises from the possibility that the shielding and the wires connected to the potentiometer are somehow of a different potential to ground. This in fact could happen if you don’t do a decent job of soldering the wires, leaving some resistance. This can cause the wires and the shield to have a different resistance to ground, causing the possibility of one or the other “coupling” with an AC noise signal, offering the opportunity to inject noise into the circuit. The term “coupling” simply means that one of the parts is either closer, or more tuned to the frequency of the noise, setting up a differential between itself and ground equal to the amount of AC current induced on the part. Given that this is exactly how the guitar itself produces sound, you’re basically applying this noise at the output of the guitar, hence that inevitable hum. However, if the part is truly grounded, there can be no potential difference between the two parts. Ground is ground, you cannot make a grounded device go positive or negative in any way, else it wouldn’t be ground, would it?

The idea of a “ground loop” is different. There is some concern here, as many a guitarist over the years plugged in his guit and was killed the minute he started playing. This is actually caused by either a fault of the amplifier or a fault of the house wiring. The guitar itself has nothing to do with it, however there are a few things that can be done in an effort to minimize the likelihood of it killing you. If however, you don’t gig, and trust your gear not to kill you, you shouldn’t need these modifications to the guit, and they can definitely affect the tone, so you should consider all likelihoods, and choose the best option for your situation. I’ve chosen not to bother with any modifications to the original Fender design, and also have chosen not to worry about some phantom theory that I can’t logically explain.

So, the first thing I did was to add a good ground lug to the inside of the guitar. This consisted of a standard, tinned StakOn lug that I happened to have somewhere in the barn. I’ve got lots of loose bits and pieces in the barn. You know, “I’ll need that someday”, and into a drawer it goes. 99.9995% of those objects will still be in that drawer when you die. However, occasionally you can find a use for one of them. But just think of how after you’re gone,  your heirs will relish in how they now have partially used starter motor brushes from a 1964 Rambler American!

So I now take a wood screw, electrical lock washer (*internal teeth to bite into the metal that they will be in contact with), and find a good location in the controls cavity. I chose the vertical side where the hole is drilled for the spring retainer ground wire. This is probably the best place, as it’s away from the electronics and the screw won’t go right through the finish on the outside (which it would have, had I chosen the bottom of the cavity. So, I put the lug on the screw, and then the lock washer, and then screw everything to the side of the cavity, right through the copper shielding. The lockwasher makes sure that I have good electrical contact with both the lug and the copper shielding, as when it’s tightly sandwiched, the teeth bite into both the copper and the lug. Once it’s in, I verify I have a good ground by checking with an ohmmeter between the lug tab and the copper foil. Zero Ohms is the goal, and I have zero!

Once it’s in, I cut two lengths of black hookup wire about 7-10 inches long, strip one end of each wire and tin it (melt solder onto it). That complete, I then go ahead and solder both to the solder lug. One of these gets passed through to the spring retainer, while the other will go to the back of our volume pot. Here’s what it looks like:

Ground lug with grounds attached

Ok, so that’s done. We now trim up the other end of the spring retainer wire to length and solder that to the retainer. What I did was to pull it all the way through so that there wasn’t any slack, mount the spring retainer using the two screws, and then trim and strip the wire with some extra so that I could handle it. I then soldered it to the retainer, and just pushed the 2 inches (or so) of excess back into the controls cavity.

Ok, let’s deal with the pickguard and associated electronics now. First, we need to remove one of the wires from each pickup so that we can wind them around each other in a spiral or twist. This helps reduce the “coupling” I mentioned earlier. What happens is that if one of the two wires is closer to the source of noise than the other, one will have “more” noise on it. In actuality, it simply has better reception, so to speak. Because the two wires are carrying different levels of AC current on them, this will produce the familiar hum. By winding the wires around each other, you stop this potential difference in two ways: first, you make the likelihood of one being closer unlikely, and second by doing this you’re basically creating a very weak transformer. A transformer works by creating a magnetic field (like an electromagnet) in one coil of wire, which then induces current in the paired coil of wire. So, when you do this same thing to the pickup wires, you’re basically pitting one of the coiled wires against the other, so it’s like 2 transformers fighting each other (hey, isn’t that a movie?). The magnetic field of one wire pushes against the magnetic field of the other, effectively canceling out the noise. This doesn’t happen with the pickup, as the change in current is only applied to the signal wire, and not the ground, so there is no opposing magnetic force.

Wrapping the wires is simple if you putting in new pickups, as you can just put them in that way. Otherwise, you’ll need to unsolder one of the two wires, snake it around the other as far as you can from pickup to controls, and then solder it back to where you took it off. I recommend doing one at a time so that you don’t confuse which wire goes where. You shouldn’t need to do a lot of turns. It should be at most 1 turn every 1 1/2 inches or so. Less is fine, but make sure that you have enough so that the two wires of each pickup stay together.

Ok, so now we just need to connect the two wires from the input connector, and the wire from our ground lug and we’re done with the electronics. Connect the black wire or ground wire to the input connector that connects with the sleeve of the connector. You can test which is which using an ohmmeter, but in most cases you can see that one of the tabs/lugs connects to the tip, while the other one doesn’t. The ground tab/lug is the one that doesn’t connect to the tip connector. Solder the other wire, or signal wire to the tab/lug that connects to the tip connector. Once again, you want to wrap the wires around each other, just like we did with the pickups. Now, thread the two wires through the hole to the controls cavity. Then just solder them to the appropriate places on your controls. In a standard strat, the black wire will go to the back of the volume pot, and the signal wire will go to the lug on the volume pot. While you’re soldering the ground wire from the input, you can also solder on the ground wire from the lug that we added to the controls cavity. That way, we’ll know that the two are bonded electrically. That’s it! We’re done with the wiring!

Here’s what the finished wiring looks like:

Wiring the electronics

By the way, you can click on any of the images to get the larger version.

Ok, so the last thing to do with our project is to insulate the interior to keep our electronics from shorting against sides. The most important places to do this are the bottom of the controls cavity and the side of the control cavity where 3-way or 5-way switch is closest. You can pretty much use any electrically insulating material to do this, just make sure it’s reasonably durable, and will stay in place. In my case, I really liked the look of the copper, and didn’t want to hide it, so I chose clear plastic. Again, I happened to have a fancy, spiral bound brochure from a tradeshow with a clear, flexible, plastic cover on it. I merely cut it to the size and shape of the controls cavity, and dropped it into the bottom. It’s actually in this picture, but I couldn’t get my camera to show it:

Controls cavity with clear insulation

Controls cavity with clear insulation

Ok, so that done, we can now put the pickguard back on. When placing the pickguard, you’ll need to be careful to route your pickup wiring from each pickup through the routes provided to the controls cavity. It may work just fine if you happen to pinch a wire between the guard and body, but over time, with all of the extreme rocking-out you’ll be doing, you’ll be liable to damage the wiring. Just take your time, and using a pencil or chopstick or something, make sure that all of the wiring falls into the slots as you apply your pickguard. Once everything’s neat and in place, align the screw holes and attach it.

That’s pretty much it. Put your bridge in and connect the springs and apply the spring cavity cover (and attach the neck if it’s detached) and it’s ready for a setup!

In the end, I chose to not shield the pickguard any more than it already was. There were basically four reasons for this:

  1. There’s some debate as to whether this affects tone
  2. The controls cavity portion is already shielded, and the only remaining part that would be affected is the pickup wires which we twisted, so the effect would be minimal
  3. I’m lazy.

So the idea is that if after complete I’m still unsatisfied I can always do it at a later date. Additionally, I’ll probably swap the pickguard out at some point for either a pearloid or tortoise shell one, so I can easily shield it at that time anyhow.

So it’s complete! It still needs some tweaking in the setup, but for the most part it’s a keeper! I was testing it out in my music room, and turned on the florescent lights and I turned on a dimmer control lamp, and I could only hear a very slight hum in the bridge position. And as a comparison, I then unplugged that, and plugged in my single-humbucker Bullet Squier, and got an IMMENSE amount of hum! Which, as soon as I put my hand on the bridge, went away, validating my plan for grounding the bridge itself. Here’s the finished product:

The Completed Strat!

So I’m very happy with the result. It definitely sounds as nice as my MIM, although perhaps just slightly sharper, which is fine by me. It stays in tune, is very quiet, and sounds amazing. If you’re going to do a project to a Squier, then this is the one to do. All told, the final actual cost of the guitar was around $140, but again, I traded the two pedals, plus I have a second guit to show for it! So, in the end, the total out-of-pocket was $140 or so, but I traded 2 pedals in lieu of $70 that I wasn’t using, and ended up with a second bullet that’s probably worth $50, so in the end I’m really only out about $20! Even adding in the 2 pedals, that’s still only $90. So if it gets hurt, stolen, or I feel the need to pull a Townsend or Hendrix-after-Who, I’m more than comfortable with the loss, and can always do it all over again – but next time even better!

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.