ocd drive pot behaving funny?

[bagudan]

Hi. just built a ocd overdrive clone from a vero layout. I works fine, until the drive pot gets past 2 o´clock. Then the signal starts to break up in to pieces ( Da-ga-da-ga-da-ga) Weird, I know. But thats what it sounds like. BTW, the weird sound only occurs when i strum the guitar. If I turn it further clockwise, the "breaking-up-sound" becomes faster.?
Whats up with that?
I would post a picture of the schematic, but apparently I´m to stupid to get it to work. (both drive pedal and posting pictures...)

The schematic is made buy "Stratorasto"
The IC is a TL082
The drive pot is a 1meg audio

[aziltz]

Hi. just built a ocd overdrive clone from a vero layout. I works fine, until the drive pot gets past 2 o´clock. Then the signal starts to break up in to pieces ( Da-ga-da-ga-da-ga) Weird, I know. But thats what it sounds like. BTW, the weird sound only occurs when i strum the guitar. If I turn it further clockwise, the "breaking-up-sound" becomes faster.?
Whats up with that?
I would post a picture of the schematic, but apparently I´m to stupid to get it to work. (both drive pedal and posting pictures...)

The schematic is made buy "Stratorasto"
The IC is a TL082
The drive pot is a 1meg audio

double check the value of the cap to ground from the feedback loop where the drive pot is.  i was experimenting with values there and too little gave me what you describe.  Stratorasto calls for 68n, but i've also see it with 100n.

[bagudan]

thanks. I´ll try that later tonight. Will let you know how it works

[bagudan]

Hmm? I tried different values for the cap you mentioned. Changing it for a 100 n made it worse, so I decided to go the other way, and ended up putting in a 15nF cap. Now I can turn the pot fully clockwise, and the cirquit sounds okay. But still? 15nf is a lot different from a 68nf... Am I missing out something here?
Seems the sound is close to the original, but maybe less drive?
-Kasper

[bagudan]

heres a link to the schematic by the way
http://4.bp.blogspot.com/_y4AYtND8Hz8/SGs-_zgfRKI/AAAAAAAAAMA/8IMJgYSyobE/s1600-h/OCD+Scheme.jpg
the 68n cap in the top left corner, is now subbed for a 15nf

[kurtlives]

That cap is alter the frequecny response of the whole pedal basically. Doubt it will help you.

[bagudan]

Not that good with schematics here, just changed it, because the other guy suggested to change the value "of the cap going to ground from the feedback-loop where the drive pot is". Isn´t this the one?

[BAARON]

Did you include the caps where it says "2x10uF"?  (You can use a 22uF instead if you want, obviously). If you don't put those in there, this circuit can do some straaange things, and what you're describing sounds sort of like this.  I know this from experience.

[bagudan]

I used a torchy vero layout, and did put in 2 10uf (c4 and c5)electro caps. Should this be 2 times 22uf el. caps?

[solderman]

Did you include the caps where it says "2x10uF"?  (You can use a 22uF instead if you want, obviously). If you don't put those in there, this circuit can do some straaange things, and what you're describing sounds sort of like this.  I know this from experience.

Hi
No yo cant subb to 1 22uF (C4 and C5) cause one is for the Vb+ and the other is for V+. They has 10K R between them.
BTW the chem and the layout has different value for the R following the 68nF cap. I have built 6 of this one always used the 4K7 instead of the 2K2 for R2 only for sound reasons. But when i tried the the different R2 I didn't experience what you do but I might not have tried that much before i decided the sound with 4K7 was my choice.

Se the differens for R2 and mark that the C7 is a Not Polar that is not an Electrolyte rather a poly.



And


//Solderman

[BAARON]

Whoops, solderman is right there... Yeah, I misread that part of the schematic.  I thought the "2x10uF" was actually just saying to put two 10uF caps in parallel in the place of C4, which would have been stupid.  Thanks for posting that version of the schematic with everything numbered - that makes it easier.

[bagudan]

Thanks for the suggestions, to all of you, will try to put in another value resistor for R2 tonight, will post how it goes.
-Kasper

[aziltz]

hi,

sorry you're having troubles here. 

My first suggestion/post about the 68n/100n was for C2 from your schematic.  I got the motorboating/gated sound when messing with that trying to add a bass control to the distortion by varying cap values there.

other than that, i think the other poster was suggesting to check the power filter caps, C7, C5 and C4, which I think you checked already.

For the record, I built this on bread board using the same schematic and it seemed to work find as stock.  i know this doesn't help much, but I believe the schematic to be at least stable if not correct.

good luck!

[bagudan]

Hmmm. 5 hours spent debugging, and finally succes:) But I am embarrassed to have wasted your time... I found a shorting trace between the legs of r8, so it was acting as a jumper
But thanks for all the help and suggestions, next time I will use my magnifying glass, before posting, but in defense, it was a small trace:icon_wink:

[aziltz]

Hmmm. 5 hours spent debugging, and finally succes:) But I am embarrassed to have wasted your time... I found a shorting trace between the legs of r8, so it was acting as a jumper
But thanks for all the help and suggestions, next time I will use my magnifying glass, before posting, but in defense, it was a small trace:icon_wink:

no harm done!

[sly]

Im assuming C10 is supposed to be the 1uF Tantal Capacitor as shown in the schematic and not the 100uF shown in the PCB diagram at the top. 100uF seems like overkill.