What Kind of Pot is This?

[some_dude]

Here's a question for you.

I was opening up my guitar to take a look around. The things a stock Stratocaster, never been modded, but the middle pickup is dead so I now have to do somthing with it...

...anyway, the two tone pots are somehow stacked. Not like a push pull pot, but are split in the middle (ie, on the dial 1-4 is one pot, 5 is both, and 6-10 is another pot).

The one pot seems to be a treble bleed, and the other a bass bleed. One has a resistor and a cap connected to ground, the other only has a resistor to ground. This pot sounds like a normal pots 10 position in the 5 position. Now that I know this, I can hear the tone change when amped and I change from pot to pot.

My question is; has anyone seen anything like this before? And where can I find some more to stick in my other guitars?

 

[HolyDirt]

Re: What Kind of Pot is This?

Yes I have.Fender used,(uses-I haven't opened one up in a few years) stacked pots in the Plus series,(I think they are called concentric-but I'd wait for Artietoo to read this thread first before saying for sure).
The idea was to create a wide sweeping tone.The two parts,(seperate pots),were linked for different sweeps.IMO-I never saw a big deal with it.
You can replace those with standard pots if you want.
The guys at Soundworks may have those,(plus if you live on base they're the closest) 546-9999.
I don't know if Gord over at the Guitar Shop deals with a lot of electronic parts 531-3390.But the guys at Centerstage have a pretty good stock of oddball & wiring parts 547-2469.
The other 2 stores don't really deal with that sort of stuff.

concentric pots are liek this, but these arent concentric, concentric pots have 2 turnable shafts, i believe this is a tbx control, its supposed to be used to blend bass to trebble... i think?

 

[Artie]

Re: What Kind of Pot is This?

Thanks for the vote of confidence JohnJohn.

It sounds like a balance, or "blend" pot. It has two stacked pots, (one shaft), and both only have a carbon element that goes halfway around the rotation of the pot. So in the middle, you have no resistance, then dial some in, as you turn either direction.

Sounds like an interesting idea.

 

[some_dude]

Re: What Kind of Pot is This?

concentric pots are liek this, but these arent concentric, concentric pots have 2 turnable shafts, i believe this is a tbx control, its supposed to be used to blend bass to trebble... i think?

That's what it does alright. I played for years with my tone set on 5 (there's a little notch there so you can feel it click in) because that's where I thought it was supposed to go. Then, after joining some of these forums, I found out that most people use their tone knobs set to 10, I was overseas at the time, but when I got home I tried it out, right after I bought a new (used) guitar.

I couldn't figure out why on one guitar, it sounded best on 10, but on the other, it sounded best around 5 (single coils turn to glass cutters on 10).

Either way, I think I've figured it out now. I think I might try and find some more of these pots, as the ability to dial out bass is kinda handy at times.

 

[Bones]

Re: What Kind of Pot is This?

Man, I was dooped into coming into this thread!

 

[HolyDirt]

Re: What Kind of Pot is This?

*swish*

 

[some_dude]

Re: What Kind of Pot is This?

Okay,did a little background.
It's called a TBX control and was first developed for the '83 Elite.
It uses concentric controls for tone shifting to control the high end of the neck pick-up,(on the Elite).
Turning the knob clockwise from the mid click position is supposed to cut off high frequencies,going the other way it is supposed to enhance the high's .(source-The Fender Stratocaster by A.R.Duchossoir,pg 60).
On the lower pot,(the one right up against the pickgaurd),just pull wire off of the middle lug and rewire as a normal tone pot,or however you want it,if you want to get rid of the TBX.

This ones on an '89 H.M.

Does that book have any good info on the H.M. series? If it does I might try and find it, but if it's only a paragraph.....

I wonder how it enhances the highs? I figure it was somehow reducing the bass, it only has a resistor on the one pot after all.

 

[Kent S.]

Re: What Kind of Pot is This?

Okay,did a little background.
It's called a TBX control and was first developed for the '83 Elite.
It uses concentric controls for tone shifting to control the high end of the neck pick-up,(on the Elite).
Turning the knob clockwise from the mid click position is supposed to cut off high frequencies,going the other way it is supposed to enhance the high's .(source-The Fender Stratocaster by A.R.Duchossoir,pg 60).
On the lower pot,(the one right up against the pickgaurd),just pull wire off of the middle lug and rewire as a normal tone pot,or however you want it,if you want to get rid of the TBX.

Thank you, I couldn't get to it fast enough ...the way the TBX works is that the upper pot is a 250k-A pot from works like a normal tone control from 0~5, at 5 (detent) it is a no-load condition that extends all the way up to the 10 position (i.e. the cap [.022uF I think] is out of the circuit),however they load the crap out of the pups by using that 82K resistor which parallels the volume pots resistance to ground ,effectively lowering it, and loading down the pups ... and here is where the other section comes into play ...
The lower section is a 1 Meg Linear pot that is a direct short from the CCW lug to it's wiper, then from center detent on up it increases the resistance (up to 1Meg) between the 82k resistor which is hooked to ground, what it does in lessen the load on the pups, which aloows the resonant peak to become a bit more pronunced ... the guiatr becomes a bit brighter, and has a bit more volume. FWIW, it's finda a dumb way of doing it, however in fenders defense it was created as a compromise for use both with their actuve preamps, and there passive systems. If you want the bass cut then there is a much better way to go about wiring it. If you want a more traditional tone knob and want to chuck it, get a fender 250k no-load pot, that will swing fron 0~9 and then at 10 hit no-load which takes the pot out of the circuit (no highs lost from the tone pot). The TBX will not work like a normal tone just by taking the resistor off, from 5 and up it will do nothing then ... kinda a waste. There are other things you can do with them though.

 

[Kent S.]

Re: What Kind of Pot is This?

I've really got to tighten up my typing ...

 

[some_dude]

Re: What Kind of Pot is This?

Hmm. That makes sense, and as I relisten to it that description is how it sounds. It's not really removing any bass, but is increasing the brightness of it.

The only thing is that the top and bottom pots in you're description both have 82k resistors, while the pots in my guitar have two different ones.

I have to go to work right now, but when I get home I'll post a pic and try and find a chart so I can find out what each resistors rated at.

You said the TBX was a compromise system. Would you consider it better or worse than a standard pot?

What are these other things you can do that you mention?

 

[Kent S.]

Re: What Kind of Pot is This?

Hmm. That makes sense, and as I relisten to it that description is how it sounds. It's not really removing any bass, but is increasing the brightness of it.

The only thing is that the top and bottom pots in you're description both have 82k resistors, while the pots in my guitar have two different ones.

I have to go to work right now, but when I get home I'll post a pic and try and find a chart so I can find out what each resistors rated at.

You said the TBX was a compromise system. Would you consider it better or worse than a standard pot?

What are these other things you can do that you mention?

There is only one resistor, but it is connected to both pots via the way it's wired (well it's connect to your signal , and that's connected to both pots).
The compromise is that the values chosen are a compromise for the impedance differences of the passive pups, versus the active pre/amp (or pre/amp - mid boost ) systems that fender used on the strat elite (dummy coil buffered along with coils to eliminate changing the pups Z), the Buddy guy, and Eric Clapton Starts, and some others I think.
There is a better way to obtain a brighter sound, still *5* on the tBX is equal to a 250k no-load pot at *10* (which is equal to no tone pot circut period) if you clip out the resistor; however then the control does nothing from *5* to *10* ... a waste.
I'm not sure what you are talking about as far as it having two resistors? The TBX has on 82k resistor, and one .022uF cap ... you can buy the TBX control as a separate kit, and that's what it comes with ... the control itself, the cap, and the resistor ... no installation instructions though, that was kinda dumb of them ... :yell:
Here are a few tricks that you can do with the TBX pot, note all values are to be adjusted per the given efect you are trying to obtain. I' try to post more on it latter. Grab this image as I only leave 'em up for a few days (server load).

 

[some_dude]

Re: What Kind of Pot is This?

I'm not sure what you are talking about as far as it having two resistors? The TBX has on 82k resistor, and one .022uF cap ... you can buy the TBX control as a separate kit, and that's what it comes with ... the control itself, the cap, and the resistor ... no installation instructions though, that was kinda dumb of them ... :yell:

I'll pull that pic in a few hours, once I'm at home.

I'll post one myself, it should explain things better.

 

[Kent S.]

Re: What Kind of Pot is This?

I'll pull that pic in a few hours, once I'm at home.

I'll post one myself, it should explain things better.

Cool ... Please do, because unless Fender changed it ,or did something a bit nutty on it (a transitional wiring or some such thing), it should be as I stated ... *IF* it's a TBX control. I know that they used concentric controls on their old Jazz basses for volume and tone, and you could most certainly utilize that type of pot differently. Also not sure what was in the HM series ... you don't have an active system in there do you? Some of their active mid boost/gain boost systems have two separate resistors coming off a pot (that may be center detented), you don't have that one do you? I don't remember that being a dual-ganged pot though .
If so that's not a TBX, and I think that the schematic shown on gearhead is wrong for those showing that type of layout (looks like they left off something, don't quite remember) ... please post that picture. ;-)

 

[Fresh_Start]

Re: What Kind of Pot is This?

Either way, I think I've figured it out now. I think I might try and find some more of these pots, as the ability to dial out bass is kinda handy at times.

I've got a Fat Strat wired up with a master tone control and a bass cut like G&L Legacys and like it a lot. It doesn't work the same way as a stock TBX, but if you roll off treble (tone) and bass (bass cut) it effectively boosts the mids. The nice thing is that you've got separate control over the bass/treble mix - I generally want different things for different pickup selections, etc. It's especially cool to boost the bass on your amp, then cut it on the guitar until you want some driving upmph! for a particular passage.

I'd love to see pics/drawings of that Fender wiring too. Is it set up so each "tone" (or TBX or whatever) works for different pickup selections ?

Chip

 

[Kent S.]

Re: What Kind of Pot is This?

I'd love to see pics/drawings of that Fender wiring too. Is it set up so each "tone" (or TBX or whatever) works for different pickup selections ?

Chip

That's what i'm wondering to as he stated something about the neck pup, ...I guess we'll see shortly ... :fing2:

 

[some_dude]

Re: What Kind of Pot is This?

Well, my camara died, so I'll post pics tommorrow once I get some replacement batteries.

Basically, it's wired up according to the stock schematic, except that there is one difference;

- There is a ? 4700k ? resistor (Yellow, Purple, Green, Gold) wired in parallel with the cap (both going from lug to ground).

 

[Kent S.]

Re: What Kind of Pot is This?

Well, my camara died, so I'll post pics tommorrow once I get some replacement batteries.

Basically, it's wired up according to the stock schematic, except that there is one difference;

- There is a ? 4700k ? resistor (Yellow, Purple, Green, Gold) wired in parallel with the cap (both going from lug to ground).

Yeah that'a a 4.7Meg (5%) resistor, not sure what they are doing with it there ... again I'd have to see how it's wired.can't imagine why they are trying to bypass the cap with a resistor, unless they are trying to load the system even more as the tone is turned down ... :wrf: I'll wait for the picture, whats the pup layout (H/S/S, H/S/H), and what are the pups DCRs?
The volume pot 500k? One tone or two?
Let me see the image first before delving into that, you did say it's an HM series right?

 

[some_dude]

Re: What Kind of Pot is This?

Is there a way to tell the resistance on the volume pot? Since it's in a Strat, so I've always assumed it was 250k.

It's a S/S/H, 1 volume, 2 tone. The top tone is wired to both singles, the bottom is wired to the HB. The HB is also has a factory split, so position 4 on the selector gives you middle and full bridge. It came stock with two unknown Fender single coils (don't know if helps any, but I'm guessing they're pretty hot as they ballance well with the HB) and a DiMarzio Super Distortion.

What's a DCR?

 

[Spark]

Re: What Kind of Pot is This?

Man, I was dooped into coming into this thread!

Yeah, I was hoping this was a KB thread :smoker:

 

[Kent S.]

Re: What Kind of Pot is This?

Is there a way to tell the resistance on the volume pot? Since it's in a Strat, so I've always assumed it was 250k.

Yeah, disconnect the CW (hot) lug of the volume pot, and place a DMM set for resistnce across the CW and CCW lugs, and read the resistance, although many pots are marked with the resistance/impedance on their sides.Most strats with a HB probably have a 500k volume control, I think the HM series did have exactly that ...

It's a S/S/H, 1 volume, 2 tone. The top tone is wired to both singles, the bottom is wired to the HB. The HB is also has a factory split, so position 4 on the selector gives you middle and full bridge. It came stock with two unknown Fender single coils (don't know if helps any, but I'm guessing they're pretty hot as they ballance well with the HB) and a DiMarzio Super Distortion.

Which tone is where? Is the stacked connected to the N+M or the B HB?

What's a DCR?

DC (Dirrent Current) Resistance, it's what your meter will measure in resistance mode (ohm mode), you can measure the resistance of the pups by hooking one lead to one the pup's hot, and the other lead to the pup's ground ... but you have to disconnect one side of the pup from the rest of the circuit ... this can be done depending on switch settings 9a pup in it's off position), or by disconnecting either the hot, or ground side form the circuit, same reason that you disconnect the pot so you can measure it. If you don't it treats all connected things as one total resistance, and gives you a flase reading ... JSYKIYDA (just so you know if you didn't already).
But we realy don't need to go there yet, just post that pic, or find a coorect schematic to post to the board. :cool3: