TS808 Tubescreamer Tone Control Not Working

[MetalUpYerEye]

I built a TS808 Clone. The tone control isn't working. Everything else works perfectly but the tone control does absolutely nothing.

Here's the checklist...
1.What does it do, not do, and sound like? Volume knob works, Gain knob works, Switch works, input/output jacks work, circuit works, TONE KNOB DOES NOT DO ANYTHING.
2.Name of the circuit = TS808 Tubescreamer
3.Source of the circuit (URL of schematic or project) = http://www.generalguitargadgets.com/index.php?%20option=content&task=view&id=90&Itemid=118
4.Any modifications to the circuit? Some very minor parts substitutions but no modifications.
5.Any parts substitutions? Yes. The tantalum caps were replaced with film caps, but the values are the same. Also a 50pf cap was used in place of the 51pf in the schematic because I couldn't find a 51pf.
6.Positive ground to negative ground conversion? No.

The circuit and everything works fine, only the tone control does nothing. I checked the wiring on the pot lugs and their connection to the circuit and everything seems to be in order. When turned on, the effect sounds the way I would percieve it to sound with the Tone all the way up, only turning the tone knob does nothing to change it.

[ncc]

I looked at the circuit and the only thing
that comes to mind is this.
Did you check the polarity of the tone capacitor?

ncc

[fixr1984]

did you try changing the pot? Maybe you have a bad one.

[twabelljr]

   If the pot checks good, make sure that R11 is grounded and good. Seems like the unwanted frequencies are not getting shunted to ground.

[johngreene]

That would seem to indicate that:

1. bad R20 pot.
2. Lug 1 of R20 is not connected.
3. Lug 2 of R20 is not connected.

--john

[MetalUpYerEye]

John and Fixr1984- I haven't checked the pot, once I have time i'll unsolder and test it and report back with my findings.
Twabell - I checked out R11. Its on there quite sturdy and there seems to be no problem with the connection (possibly cold solder joint?)
NCC - I changed the caps from tantalums to films, i thought films didn't have a polarity (am i incorrect?)

[twabelljr]

    If you used a film cap for C9, it probably is not polarized. Look close to make sure though. When you check the pot and all it's connections make sure your circuit is good from the middle lug down to C9, then to R11, then to ground. Looking at the schematic, if this branch of the control does not go to ground, the control will not work. Then, of course, make sure the other lugs are connected properly to the board and its relevent circuits around IC1b are all intact.

[JJ]

Gday,

Not sure if you found the solution but I found this post in a search as I had exactly the same problem when i finished my ts808 the other day (my first build), eventually I found I had put the wrong value caps in the tone section (0.022's instead of 0.22's). I'm Just not used to reading the figures on the film caps. Anyway found this mistake after trying all the above suggestions, and when double checking to see if there were any polarity markings noticed that the physical size of caps were the same as the .022's on the input - doh.

anyway  thank you to the above posters for the suggestions, and hope you find your solution