madbeanpedals::forum

Projects => Tech Help - Projects Page => Topic started by: mjcyates on December 20, 2011, 02:56:09 AM

Title: Dirt Bag V3205 Question
Post by: mjcyates on December 20, 2011, 02:56:09 AM
So I have my Dirt Bag (V3205 version) built. Everything works except there is no delay. Bypass is fine. Effect engaged = leds working and signal passing however no delay. The level knob works. What's the most likely culprit?
Title: Re: Dirt Bag V3205 Question
Post by: mysticwhiskey on December 20, 2011, 03:09:59 AM
Barring a build fault (solder bridges etc) or component failure, it might be a biasing adjustment issue.  There's a relatively narrow range of adjustment of the bias trimmers, outside of which there will be no signal passed through.  If you have an oscilloscope or audio probe this is fairly straight-forward to adjust for each chip (apply a signal to the input and probe the output of pin 3 for each chip while adjusting the corresponding bias trimmer for minimal distortion).  The build doc has a good method for calibration.

Also check your ICs' orientation, and perhaps measure and post your (DC) voltages for each pin of each of the ICs.
Title: Re: Dirt Bag V3205 Question
Post by: mjcyates on December 20, 2011, 03:55:45 AM
Thanks, glad to hear that as I have not put much effort into biasing yet. I didn't realize it would be that finnicky.