GroovyDude Blog

Replicating Fender's "no - load" tone pot.

2008-04-27T15:57:00Z

Here's a cool and easy little mod you can easily do youself. I found this online awhile back, tried it, and thought I'd post it here.

Myself, I do use the tone control on my guitar. Potetiometers are simply variable resistors. They contain a wafer which has carbon deposited on it, and when the knob is turned, a wiper drags across the surface and varies the resitance. The closer to 10 on the knob, the less resistance. However, even at maximum, there is still some resistance. The lower the pot value, the more the load. This translates to a reduction of signal that makes it to your amp, and a reduction in the higher frequencies. The tone knob is the bigger culprit since it has anywhere from a 0.020 to a 0.100 microfarad cap attached and going to ground. And even when the control is a '10', it is never completely out of the circuit.

For some, the solution is simply clipping the wires to the tone pot, rendering it useless. Then Fender came out with their "no - load" tone pot, which works great, but is only available in 250k (I prefer 500k), and it clicks when the pot is turned to ten. Once it clicks, it is removed completely from the circuit. It works because once it clicks, the wiper is removed from the carbon contact, which forces the signal to go straight from the volume control to the output jack. It works great, but I like to do swells with my tone in kind of a faux-wah sound, so the clicking action didn't work for me.

So the solution for me is to take apart the tone pot and remove the carbon from the wafer where the wiper would be at it's maximum setting. See below:

Tone pot installed (the one closest to the jack).

Sorry about the flash, but you can see the wires removed, and it was only necessary to remove one side of the capacitor.

I used needle nose pliers to lift up the tabs on the side of the pot

Disassembled pot. Make note of how it went together, of course. The part we're concerned with is the wafer, which has cap attached. The carbon deposit which generates the resistance is the black circular area which joins the outside two lugs.

I used an exacto knife and a needle file to remove a very small amount of the carbon deposit. Now the wiper will not make contact with any of the carbon when set at the maximum position. This will open the connection, causing the pot to be completely removed from the circuit.

Reassemble and reinstall. It you have some tuner cleaner, shoot a bit of that in there to clean out any stray bits of carbon and relubricate the pot, and enjoy the extra bit of gain and high end that was previously not there!

DIY wax pickup potting

2007-11-28T21:36:00Z

Most guitarist (and some bassists) who've ever played using a lot of volume, gain, or both knows all too well about that microphonic squeal that can plague a gig. So you end up rolling the volume back during quiet passages, although some squeal always ends up getting through. Listen to Randy Rhoads at the beginning of Crazy Train for a great example.

So what causes it? First you must make sure it's the pickup. Try your guitar with a different amp. If it's definately your guitar, make sure there's not some loose metal, such as a pickup height spring, that's not vibrating sympathetically. Your pickup will transmit that sound to your amp, and it sounds just like a microphonic pickup. If I eliminate everything else, I'll remove the pickup from the guitar, and wire it to a jack. Plug it into the amp, and adjust to normal settings. If it still squealing, then the coils are vibrating.

So do you just chuck it and spend $150.00 or more on new pickups? While I recommend being prepared to do just that, you can always try potting.

Pickup potting is simply using some substance to "seal" the pickup and prevent the coils from oscilating. Using wax is not difficult, and it's cheap. You could pot a dozen pickups with about $10.00 worth of materials.

There are some pickups that cannot be potted. Any that have already been potted with epoxy cannot be repotted, such as all variations of EMG, Shadow, and Bill Lawrence. Pickups that have been potted with lacquer will be very difficult, and generally will only show slight improvement.

Good candidates are pickups that come on imports. Epiphone pickups sound pretty good to my ears, as do the "Duncan Designed". Ibanez pickups are manufactured by DiMarzio's overseas manufacturing, and are not too bad either. Any pickup that you believe sounds good that doesn't fall into the categories in the previous paragraph are good candidates.

This customer has a set of Gibson 57 Classics. He loves the tone, but they are manufactured the way they were in 1957, with no potting at all. They squeal badly even with the moderate amount of gain he uses.

As stated before, you should be prepared to replace the pickups prior to attempting potting. The pickup can be damaged to the point of non-functionality, although I've never had one go bad during the process.

So here we go. You need the following supplies: double-boiler, parrifin wax, beeswax, dowel rods & rubber bands.

A double boiler is a pot in a pot. I don't have one, so I made one out of a metal coffee can. I drilled four holes, and ran dowels to support the can so it doesn't touch the bottom or the sides of the larger pan. The dowel on top is to support the pickup in the wax without it touching the sides or the bottom. The extra hole in the back is a drainage hole, in case I melt too much wax.

You use an 80/20 mix of parrifin and beeswax. The reason for the beeswax is parrifin by itself hardens too solid when cool, and can flake off. Beeswax keeps it flexible enough when it hardens to prevent that. I used 1 lb of parrifin, so 20% is 3.2 ounces. I uses probably closer to 4 oz. A perfect 80/20 mix is not imperative.

Fill the large pot with water. Fill it up as full as you can without the small pot floating, and turn on the heat. Your goal is 140 - 150 degrees. Anything hotter can damage the pickup. So turn the stove on low and give it time.

You can see what happens if you get distracted. I let the water boil, and the wax is 200 degrees. Way too hot!!! A pickup's plastic bobbins can melt at that temperature, as can the lacquer coating on the pickup coils. It took over an hour for the wax to cool to the correct temperature.

The water still looks like it's boiling, but it's actually wax which drained out of my extra hole.

I used an old guitar string around the dowel and through the screw hole to suspend the pickup in the wax. If the pickup has a cover, leave it on. Also leave the pickup tape on. What I didn't show is the rubber bands wrapped around the pickup. The pickup tape's adhesive will loosen at this temperature, so the rubber bands will keep it in place.
There was a rush of bubbles at first, indicating the wax was getting into the crevices just like we need. Let it sit for 15 - 20 minutes, but do not walk away! You need to monitor the temperature for the whole process. 150 degrees is the maximum.

And we have two potted pickups. Let them cool for about 5 minutes, and wipe the wax from the face of the pickup. Install them and see how successful it was. Keep in mind, if you're using a ton of gain, a lot of volume, and stand close to your amp, this does not guarantee no squealing at all, but you should have an immense improvement.

I offer this service for $10.00 per pickup if you're not comfortable with the process. Much cheaper than a new one.

Vintage Guild Bass Restore V

2007-07-27T19:41:00Z

And the finished product. The owner and I are quite happy with the result. The mahogany darkened to a very rich brownish red. And it still sounds amazing.

Oh, and I did find a pic of my 80's Kramer that I painted. It was my first real success painting. I edited most of the pic to spare you my 1987 hair band get-up, although you get the gist with my purple & black striped wristband and glittery jacket. :)

Vintage Guild Bass Restore IV

2007-07-25T23:14:00Z

The owner decided he didn't want the wine red finish like the original. He really liked the wood grain, so he requested just a clear finish. So I applied 17 coats of clear after the sealer, with light sanding between coats. Waited four days, and rubbed out the finish.

I think it's good when you can see the refection of the clock on the wall in the finish. :)

Vintage Guild Bass Restore III

2007-07-23T21:56:00Z

After doing the previous work, the owner took it home and played it for awhile. A few months later, it came back to me roughly sanded down, although there was quite a bit of yellow paint still in the wood pores. Bad pic, but you get the idea.

So, after about 4 hours with some steel wool and paint stripper, you have the next pic.

Next we do two washcoats (thinned finish), fill the grain pores with a very dark reddish brown grain filler, and the sealer.

Vintage Guild Bass Restore II

2007-07-20T20:01:00Z

We restored this bass in two phases. The initial issues addressed were a broken headstock & a new pickguard.

Most people have seen my headstock repairs before, so I only posted a pic of the after. It was more a split running roughly a thirty degree angle to the wood grain, so it wasn't as traumatic as some of the others I've done. It only required reinforcement on one side. I used my traditional graphite spline.

Next was the pickguard. This was quite challenging. The original pickguard was not available, so no template. I used the pic I found in the first post, used the largest pickguard blank I could find, and freehanded one. I think I got pretty close.

Vintage Guild Bass restore

2007-07-18T20:02:00Z

Many of us made not-so-great decisions in the 80s. With EVH's striped paint job, then the popularity of the painted graphics on Jackson guitars, many musicians tried their hand at doing their own paint work. We had varying degrees of success.

We stripped off the old finish, and used several cans of Krylon trying to make our guitars look cool. A lot of perfectly good guitars were ruined during these experiments. I personally had an import Kramer Baretta that had no less than eleven paint jobs before I settled on a modified rising sun graphic. If I can find a pic, I'll post it.

The big mistake we all made was stripping off the original finish. For some reason, we thought we had to remove the old finish before doing a new one. If you decide to attempt this yourself, be advised all that is necessary is taking some 600-grit sandpaper, and sand off the shine. As long as the finish is not damaged, you can then paint right over it. Your results will be much more professional, because you'll have a good level substrate to start with. Getting the surface level is the hardest & most time consuming part of finishing.

So we have a mid to late 70s Guild b302. It was painted a very bright yellow, and splashes of neon pink, orange, and green applied. The owner said it glowed under a black light. It's was pretty cool in its day, but completely not acceptable today. The original pickguard was replaced with a home-made plexiglass pickguard, and EMG electronics were added. I will preface this by saying this is an amazing sounding bass made of solid mahagony. You don't see bodies made of one piece of wood anymore. Two is the minimum unless you're willing to pay a very high premium.

I found a pic that gives you an idea of what this bass orginially looked like. We're going to try to bring it back to it's former glory.