DR quack HELP PLEASE

[jnee8871]

Hi

I need some advice. I can't get my DR Q to quack. I bought the board of GGG. The only sub I made was a 2n2222a for the Bipolar. I'm using a 4558 for the opamp.

It does make sound. It gives a slight quack if the sens pot is all the way off. But even the slightest increase and the quack is gone.

Also one of the LED's stays lit all the time and one is only when it see a signal...I'm wondering if that was designed that way.

I did the GeoFX layout. I have double check my values and check for bad solder issues.

I'm not sure what I should be seeing for voltage on the BIpolar. Also what part is the envelope filter and what is the amplifer...

Everything looks good...where should I start for voltages...

One note...the AMZ schematic has a 4.7M pull down resistor and the Geo does not....

Thank you

[R.G.]

Go ask at the diystompboxes.com forum. Lots of experience there.

[oldrocker]

Yes one LED should stay on all the time and the other should light when the guitar is played. Try a 3904 instead of the 2N2222. It might work better.

[oldrocker]

Well I tried a 2N2222 in mine and it worked fine. Which JFET did you use?

[cjlectronics]

I believe that pedal is based on the Dr. Q, correct? If so, years ago i fixed one of those pedals and it was doing the same thing. The problem was that someone used a 4558 when the schematic calls for the 1458. If this is the pedal I'm thinking of then replace your 4558 with a 1458 and this could very well be the problem.

I have not had the time to experiment and calculate numbers for this circuit to figure out why this is the case. Although come to think of it, Mark Hammer did this at one point

[Mark Hammer]

I didn't exactly "calculate numbers" for it, but I did try popping other chips in the socket. The DR Q absolutely requires a 1458 to work properly. The issue was not the filter section, but rather the envelope follower. Having tried about a half dozen different dual op-amps, I can say with confidence that the most pleasing sweep came from a 1458, and other types of "higher quality" op-amps either failed to sweep or gave a sweep so wide that it made the pedal unusable. Jack Orman's redesign of it that he called the Dr Quack included several modifications that were intended to make the basic circuit work properly with pretty much any dual op-amp. And it does.