While I realize that the Rhythm Circuit is not particularly popular, I do use it occasionally and want it to work properly.

On my Squier CV Jaguar, it works perfectly, but on the Warmoth build, there is a curious problem: if I roll the tone control down, it begins to decrease the volume, and at zero, I lose all volume. The tone control of the rhythm circuit on my Squier doesn’t have this effect, so I’m curious if anyone else has seen this.

The artist formerly known as: Synchro

When Surf Guitar is outlawed only outlaws will play Surf Guitar.

edwardsand wrote:

I use the Jaguar rhythm circuit often, but I've not come across the problem. Sounds like a wiring issue - can you post pics?

I’d have to pull the control plate for the rhythm circuit, and that may take a day or so to find time for.

As far as diagnostic steps are concerned, I’ll probably start with pulling the control plate out of its cavity, and test it there. It could be a short against the control cavity shielding.

The artist formerly known as: Synchro

When Surf Guitar is outlawed only outlaws will play Surf Guitar.

edwardsand wrote:

I was also going to suggest a short against the shielding - if you coated the cavity with shielding paint, it could well be coming in contact. That would be easy to test by unscrewing the control plate and lifting it out and try playing the guitar through an amp.

That will be the first step. Those control cavities are pretty cramped. It’s not causing me any operational problems, I would rarely roll back the tone on the Rhythm Circuit, but I hate to leave a problem unsolved.

I have given some thought to installing a 1 meg pot on the tone control, which would allow me to achieve a brighter tone, but before I can do that, I need to make sure that it operates properly throughout the entire range, because I will, occasionally, want the warmer sound. Maybe I should quite typing and break out my screwdriver.

The artist formerly known as: Synchro

When Surf Guitar is outlawed only outlaws will play Surf Guitar.

My opinion: don't use 1 meg or 500k for tone control anywhere. You'll squeeze all the tone control in the very end of the sweep. A 250k audio is good. If you're worried about any loss of highs at 10, use a no load pot.

If I'd stop buying old guitars to fix, I might actually learn to play.
Bringing instruments back to life since 2013.

Last edited: Jun 08, 2024 23:18:41

Thanks for the help, guys.

synchro wrote:

edwardsand wrote:

synchro wrote:

I have given some thought to installing a 1 meg pot on the tone control, which would allow me to achieve a brighter tone, but before I can do that, I need to make sure that it operates properly throughout the entire range, because I will, occasionally, want the warmer sound. Maybe I should quite typing and break out my screwdriver.

What would be the point of a 1M pot on the tone control? That would basically make it the same as with the other controls, unless there is something I've missed somewhere along the line. I dig the neck pickup in the standard mode and via the rhythm circuit, and in the latter mode, it really gives it a different character - not surf, for sure, but really cool for certain flavors of music.

So yeah, get that screwdriver out...

As it turns out, the wiring is correct, but the pots are reversed, with the 50k in the volume position and the 1 Meg in the tone. Ok, this contributes pt a very warm sound, because the pickup is only developing over a 50 kilohm impedance and that has the same effect upon the sound as if the inductive reactance of the pickup was much higher. I could actually live with that, because it makes a little pickup sound big, and it would work, if the tome control circuit was conventional, however it’s anything but conventional.

So the tone pot basically works by taking in the signal directly from the neck pickup, when the switch is in the rhythm circuit position. The tone cap is on the other side of the pot, and the wiper feeds signal to the volume control. So, when I turned down the tone control, I’m basically increasing resistance from the neck pickup + to the volume control, which yields a voltage drop in the signal.

So, this explains the whole of the problem. The rhythm circuit is very warm sounding, because the pickup is only developing voltage across a low, 50 kilohm impedance, at best, and probably closer to 35 kilohm when I roll the volume back slightly. Sounds like a Gibson with a neck P-90.

So, back to the operating table, and I’ll swap the pots. I’ll get back some treble having the pickup develop into the proper impedance and the tone control should function properly at 50 kilohm max resistance. By design, there’s some loss with this tone circuit, when the tone is rolled down, but with an 20:1 ratio between the tone pot and the volume pot respective resistances, the losses are negligible.

This is a very clever circuit design. I’ve heard that Freddie Tavares was being the rhythm circuit, so maybe he dreamed this up. I didn’t really understand it until I was preparing to write this reply and had another look at the schematic.

It obviously works well, because on my Squier Jaguar it’s flawless. It’s amazing that the brightest guitar of it’s time could be made to sound like a Jazz guitar, with just one switch.

ldk wrote:

My opinion: don't use 1 meg or 500k for tone control anywhere. You'll squeeze all the tone control in the very end of the sweep. A 250k audio is good. If you're worried about any loss of highs at 10, us a no load pot.

In this case, I can’t. The rhythm circuit is very tight and requires mini pots. I bought Fender part numbers, but the are actually CTS pots. The Squier uses Alpha, but they seem to be doing fine, and in this climate, corrosion is not a problem, do a squirt of De-Ox-It every few years should make ‘em last forever.

But you make an interesting point. A 250k no load gives you the best of both worlds; the ability to totally isolate the tone cap when turned fully clockwise, and a nice taper when rolling off the tone.

On the main, non-rhythm circuit, I keep the tone maxed virtually all the time, so the taper there doesn’t really matter to me, and one megohm of isolation for the tone cap is more than adequate to protect the highs. If I ever rewire it, however, I might just swap in a 250 kilohm no-load. I still have some laying around, from my Strat playing days.

The artist formerly known as: Synchro

When Surf Guitar is outlawed only outlaws will play Surf Guitar.

Last edited: Jun 07, 2024 00:52:36