Tone pot does not work??

[angelodp]

Some trouble shooting help if you can. On this install, volume works, I have that peter green thing going with the two pups so i will reverse the leads on one pup, but my tone pot does not work at all..... here is how its wired?? Is there something wrong here.



best ange

[D2o]

Hi Ange,

Look fine to me ... whadda ya mean when you say it doesn't work?

Like ... at all? Have you tried a different cap?

You don't mean that it's all business only when you get to the bottom end (i.e. you aren't using a linear pot, are you?)

D2o

[angelodp]

You are up early too!! HI!! I mean it has no effect at all?? Maybe I should pull the cap off altogether. What's the best routine for trouble shooting once the harness is out of the guitar. It on my workbench. Would it help if i posted a gut shot of the actual build ??

best ange

PS building a 5E3 whoopi!!

[cynical1]

I'm no guru, but it looks right to me. Just to beat ChrisK to the punch, have you checked the pot to make sure it's good?

[angelodp]

Yes pots good just checked it ??

ange

[cynical1]

Your diagram details a 500K pot and a .047 cap. Do you have a 250K pot and a .022 cap to swap for the tone?

[angelodp]

oops. I used 250k on both volume and tone not 500, I should change the graphic.... here is the guts shot

[ChrisK]

Your diagram details a 500K pot and a .047 cap. Do you have a 250K pot and a .022 cap to swap for the tone?

Why do you ask? The cap value and pot value are not interrelated.

Yes pots good just checked it ??

How did you check it?

What do the question marks (??) mean in your statement?

Would it help if i posted a gut shot of the actual build ??

Yes, this might give us additional fine focus. (hint, hint)


If you checked the pot by varying the knob and watching the resistance correctly change between the two terminals that you're actually using (just to be sure), you could try testing the cap.

The easiest way to do this is to connect your digital multimeter to the two cap leads with at least one cap lead disconnected.

Set the meter to the highest resistance range available.

Measure the resistance, it should read over-range or open. If it reads near zero (verify on the lowest resistance range), the cap is shorted.

Now momentarily short the cap leads together while they're still connected to the meter. If the reading instantly jumps to over-range or open, the cap is likely open.

If the reading increases somewhat slowly (in two or three readings or so) up to over-range or open (the ohmmeter function bias voltage/current is charging the capacitance), then the cap is likely still good.


Of course, if you have a multi-meter like some of mine with a capacitance measuring function.......


If the pot resistance varification and the capacitor chargification tests are ok, then the wiring/soldering is likely GeFooey.


Note: This procedure presumes that your hearing actually extends above 500 Hz.

If it does not, your tone control is likely working fine..... ;D ;D

[angelodp]

Hi, I did check the pot as you described and it does work. My question marks were remarking that is the pot is good then why is it not working in the circuit....I don't hear the tone change at all.

[ChrisK]

That's a mighty small physical size capacitor that you have there!

It is a ceramic cap.

Please measure the resistance of the cap across its two terminals with the tone pot set to its full-out resistance ("10") (you may need to disconnect one terminal to eliminate the effects of the other circuit components).

If the pot is 250K, you should read at least that value. If you read a value that is substantially lower, then this ceramic cap is a supply bypass cap (Z5U) and is NOT SUITABLE for analog signal usage. I have seen ceramic caps that had under 1 K Ohms of internal parallel resistance in my career as an electrical engineer.

I usually use film caps.


If the tone control causes a reduction in output level when turned down, the cap is shorted or posses internal parallel resistance.

If the tone control has no effect whatsoever, then the cap and/or pot is open at some (or all) points.

[angelodp]

Yes it is a ceramic cap and the resistance works until I reach ten on the knob and then it does not read anything. Seems like this cap was a poor choice. I don't actually even need a cap on the tone pot, is that right. I should pull it.

ange

[angelodp]

without the cap do i simply ground the center lug of the tone pot to the back of the pot?

ange

[angelodp]

I pulled the cap and checked the circuit on an amp and the tone knob seems to be doing something now. I will reinstall in guitar and report back.

ange .... thanks guys

[sumgai]

ange,

Without the tone capacitor, you have a useless potentiometer. Or worse, if you ground the other lug, you have a steep-slope volume control. Neither case is desirable.

I see you modified your original post, did you change the drawing? As of this moment (check my posting time), you show a 22pf capacitor. Errrr, that's not gonna do it. (This would also explain Chris's note about it's size.) The cap should be 0.022µf, or 22nf. What you show is fully one thousandth of what you need.

Also, the picture is in focus enough for me..... I suspect that the ground solder joint on the back of the Tone control is flaky. Note the same joints on the back of the Volume control - ooh, shiny© (copyright CEKikta 2006), no brown spotting around the perimeter of the joints. Make the Tone control's solder joint look the same, just to eliminate the possibility of trouble.

HTH



sumgai


Edit:

I've been ninja'd..... I predict at least a few tears ahead, in a future post......

[ChrisK]

Yes it is a ceramic cap and the resistance works until I reach ten on the knob and then it does not read anything.

What does "and then it does not read anything" mean?

It absolutely reads something, at all times, in this time-space continuum. The meter may not display something, at all times, in this time-space continuum, but the display of nothing means something.

I presume that at "10" the resistance reading goes to over-range or open (which implies over-range). A blank display might mean this also. Is this what is displayed when the leads are not connected to anything?


Now, are you reading just across the cap while disconnected from the pot (which would make the statement regarding resistance unrelated) or across the cap and pot that are connected in series, the combination of both being in parallel with the rest of the circuit?

If it's the latter, it would appear that you have a "no-load" Fender tone pot that disconnects the wiper from the element at "10". I presume that "and the resistance works until I reach ten on the knob" means that the resistance increases as the knob is turned clockwise up to "10" and then goes over-range or open.

It might be a good time to measure the resistance of the pot when it is set to "5". If it reads about 40K, then you have an audio taper which, IMHO, is ideal for a tone pot. If it reads 125K, then you have a linear pot (which is unlikely for a "no-load" pot).

If so, this is good, the pot is fine. We still don't know about the cap.


procedure

Connect the meter leads directly across the cap.

Set the meter to the highest resistance range available.

Ensure that the tone pot is set to "10" (disconnecting the cap from the rest of the circuit).

Measure the resistance, it should read over-range or open.

Now momentarily short the cap leads together while they're still connected to the meter.

/procedure


If the reading instantly jumps to over-range or open, the cap is likely open.

If the reading increases somewhat slowly (in two or three readings or so) up to over-range or open (the ohmmeter function bias voltage/current is charging the capacitance), then the cap is likely still good.


I've been ninja'd..... I predict at least a few tears ahead, in a future post......

[angelodp]

Here is the cap i used, wrong value huh, I goofed. i will run out and get the correct one before continuing.

[ChrisK]

That's a mighty small physical size capacitor that you have there!

Well, it still works, just at about 65 KHz (oh wait, there's a cable involved).

[angelodp]

I have a 203K500v orange drop cap, that should work.

ange

[ChrisK]

203K500v is a rare value. Are you sure?

This implies 20nF or 0.020 uF or 20,000 pF. One usually sees 223K500V

It will work.

[angelodp]

Yes its out of an amp i was working on its 203K600v, will the small difference between .020uf and .022uf matter.

ange

[angelodp]

Oh man what a silly mistake to put in the 22pf cap.... I got the correct value in there and its working fine. I will post a shot of the guitar later..... 1457 Dano with single coil Strat pickups..

Its pretty nice.

thanks all Ange

[ChrisK]

Yes its out of an amp i was working on its 203K600v, will the small difference between .020uf and .022uf matter.

Only about 10%.



;D ;D

Glad that things worked out.

(I'll bet that you'd got a really good price on those caps as well. )

[sumgai]

May 18, 2009 12:06:36 GMT -5 ChrisK said:

......
I've been ninja'd..... I predict at least a few tears ahead, in a future post......

You too, eh? Must be sumpin' goin' 'roond, like a virus or sumpin'.......

[angelodp]

Just wanted to show the end result.... This guitar has a great sound. All hand made. Neck is Birch, body is birch plywood and masonite. 72 strat & 90's pickups

thanks ange

[cynical1]

Very pretty guitar. Looks like a very clean job all the way around.

You're the second person I've seen here that made a guitar from birch wood. Maybe when I get done with all my unfinished projects I may look into this more.

Nice job. You should be proud...and if you want to send up some sound clips that's be cool too.

Happy Trails

Cynical One

[ChrisK]

You're the second person I've seen here that made a guitar from birch wood.

I remember folk back in the '60s that made stuff from birch. There was even a company that made port-o-lets from birch. Their trucks were labeled "The Birch John Society".