Power supply filtering for Wahs? Nasty noise, Help Please!!!

[BillyJ]

Ok I think I am going mad. I got a fulltone pot about a week ago brand new.
WIth a battery I am fine and dandy and am very pleased.
Plug oin the DC jack and I get this one little spot up toowards the top of the throw where the wah just goes nuts and oscillates like a fuzz factory or some other mad toy.
Why does this happen?? How can I stop it?
Is there something wrong with the pot I just bought?
I had put a diode on like Teese suggests here
http://www.realmccoycustom.com/TROUBLESHOOTING.htm
I tried holding a 100uF 16/V cap across like he suggests but it didn't help at all.
Off to Geo to re-read some PS articles but if anyone can help explain why this is happening or can help me rid my wah of it that would be great.
Can't thank everyone around here enough and lords know I don't but my gratitude is a giant!!!
Thank you all so much!

[Arn C.]

Maybe you can try readjusting the pot.  Sometimes I have noticed at the extreme throw of the pot, where I have also had some annoying sounds, so I readjusted the pot.  Loosen it up and move it a little bit the opposite direction and try it again.  It is possible that the pot you purchased doesn't work properly at the end of it's rotation.

Just something to try!

Arn C.

[BillyJ]

Hey Arn thanks!!
Bummer though I tired that and it is smack dead up 2/3 of the way!
Rotten luck! I suppose I might try another pot but I will be pissed if another pot works fine!!
Thanks you Arn....BTW can you PM me your address?

[mattv]

I doubt it's the power supply as opposed to the filter oscillating. There are component value or mechanical adjustments (as Arn suggested) that you can make to avoid this, but I don't know what they are off the top of my head. Try the Wah Tech at Geo.

[Arn C.]

I guess I may be wrong what I said in earlier post.   you did say that it worked fine with a battery.  
I always use adapters, I got rid of the batteries.   So,  I use shielded wire on my input and output jacks(ground one end only).  This seems to help me with radio, static, whatever extra noise there is.  Just something else you may try.   And is this with the pedal depress all the way down towards the front? (Treble?).  This may just emphasize the noise, it may be there all the time, but only noticeable on full treble.   Also for curiosity sake, check the input voltage with the pedal on and full treble(the place where you get all the noise), It may be possible also that you are getting much more voltage than the battery is giving you, not that that may be creating the problem, but hey, ya never know!

Arn C.

[niftydog]

I'm with Arn C, check the voltage you're getting from the power supply vs what you get from a battery.

Is the supply regulated?

[Transmogrifox]

Solder a wire to the pot case (physical chasis) then connect that to ground.  Sometimes it's just a parasitic capacitance to ground between the signal path and the pot case...also some RF problems.

if that doesn't do anything...

Read my (long) post on the thread about Vulcan Build Report.  I went in depth about RF heterodyning and power supply effects, though this is not as likely to happen in a wah.

The actual AC noise on your power supply could do that...my post will help you with that too.  Sometimes a single capacitor is not enough. You may want to use a series resistor (47 to 100 ohm), then a capacitor.

[BillyJ]

Yikes. !6V that thing is putting out. Guess it ain't so filtered.
Strange though I could not get it to happen again!
Well I guess if it comes back I will get to checking it out more. For now I thinkI will use a better adapter or batteries.
Thanks for all the help!!!