Crawls Backward (When Alarmed)

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Rickenbacker Treble Cap Switch Mod

While I have my 12-string on the bench, I'm going to do some electronic mods to it. This first one is something that was (is) done by the factory.

Older Rickenbacker guitars and basses had a small value capacitor in series with the hot lead of the treble pickup. What this did (does) is filter out bass frequencies and pass treble. The factory offers this as a 'vintage' tone switch on its vintage-style bass - a push-pull switch puts the capacitor in or of the circuit.  The 'stock' value capacitor is .0047 uF (aka .005), I think at 80 volts, but you can use any voltage rating you have on hand.

So I figured I'd give it a whirl.

Now, there is a 'factory' switch for this mod - which is a 330K pot with a SPST switch mounted on it. This is what's used on the bass, and it makes it possible to exactly duplicate the wiring as the factory does it. The guitars use a 250K pot, so 330K should work just fine, and may be a bit brighter.

Now, mind you, you can use any SPST or DPDT switch, or pot with a switch, to accomplish the same thing. I've used switches like that before on some other guitars for series/parallel and phase switching.

But I decided to go ahead and procure the Ric switch. In fact, I got 2.

One of the reasons I did it is that it's sold as having a value of 330K. The stock pots on my 360/12 are 250K, but this is close enough. But I wanted to see if I would notice any tonal difference using a 330K pot instead of a 250K. In theory, as I said above, a 330K might be a bit brighter.

So here are the two pots. One of them is going to wind up in the guitar.

Or is it?

Since 330K is a bit of a non-standard value for a potentiometer, I decided to measure them just for the heck of it.

Well, how about that!

One of them measures 483K - actually within typical tolerance of a 500K pot.


Hey, guess what?

The other one measures almost 500K!

So I have two "330K" pots that are actually 500K.

What the heck?

Are they all like this?

Is this a Rickenspiracy?

At any rate, I don't want to use a 500K volume pot in the guitar, so fortunately I can go to Plan B.

Namely, use one of these fancy new CTS pots with a push-pull DPDT switch on it. I saw them on the Stew-Mac site and snagged a few for future projects. They have them in different values; since I am usually messing with Fenders, I got some 250K pots.

Little did I know I'd use one so quickly.

The neat thing about these pots is that there's a little circuit board with through holes for your wiring - instead of tabs right on the switch. You can see the row of holes just below the pot lugs on the right.

I measured it and, hey, it measures 250K as it's supposed to.

The wiring is pretty easy.

I drew up a little diagram since I sometimes tend to forget what's supposed to go where.

And it gives me a chance to study it and make sure it will work as desired.

I'm wiring it so when the switch is up, the cap is in the circuit. When it's down, it's out.

If you read the diagram you'll be able to trace how it works.

Here's the stock wiring on the guitar.

I usually take a picture like this so if I really goof up, I can use the picture to go back to the way it was originally.

We'll be replacing the bridge (treble) volume control with the push-pull pot. The control is the one on the lower right.

You can but a whole control assembly pre-wired from the factory just like this and plop it in your guitar. Not sure why you'd need to do that, but my point is that there is great parts support directly from Rickenbacker.

Except that their 330K pot measures 500K.

I wired up the switch as a sub-assembly before installing it on the guitar.  It's wired just like the diagram, except the input and output wiring isn't there yet.

I wish I had a Russian PIO cap in this value, but I don't, so I'm using an Orange Drop. Check out the date code! This one's been around a while.

This is one place where you might be able to hear the difference in different capacitors, since the signal passes through it, unlike a tone cap.

Take the original pot out of the guitar, and wire the new one up.

And here's how all the connections are made. I labelled everything on the photo - should be clear what goes where.

One thing about these new pots is that if you use the pot itself as a ground, you'll have to solder to the side of the pot rather than the back. Works fine. I just sanded the pot a bit as you normally would to aid the solder sticking to it, then soldered the grounds to it.

Rickenbacker uses a clever (I think) way of wiring the ground buss. There is a lead that comes into the control cavity from the tailpiece, and that lead goes to the treble volume pot. Then there is a lead that runs to each of the pots in turn, but it doesn't do a full circle.

In other words, it starts at the neck pickup (bass) volume pot, over to the treble volume, then the treble tone and then finally the bass tone. There is no connection between the bass tone and the bass volume. If there were, it would be a ground loop, and potentially hum. But since it's not a full circle, there is no ground loop. Compare this with a stock Stratocaster, which is Ground Loop City.

Then we just bolt the new control to the pickguard.

Then I made another mod!

On a stock guitar, the pointer/indicator lines on the knobs all point downward when everything is turned up to maximum.

On my other guitars, the pointers are up at maximum, so that's what I'm used to. Easy enough to unscrew the knobs so they point up.

How does the mod sound? Well, to be fair, I've only tested it though my little workbench amp. But it does get a thinner sound, especially on the bass strings. I might do some maths and figure out what frequency the 'stock' value capacitor changes and see if it's worth playing with. Something like an .003 would be really thin I'd think.

Guess what? I'm not done with the electronic mods. While I had it apart, I figured I should mess with some other stuff. I'm sure I will offend Ric purists a bit. Stay tuned.


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