Tonepad MXR Micro-amp probs

[Deano]

I've just build an MXR Micro amp from Tonepad's layout.  I can't get it to work properly with the effect on.  I can't find a 500k rev. log pot but i read that i could use a 1M linear with a 1M resistor accross the outer lugs.  I did this but with the guitar plugged in and the effect on I get no sound.  If I put my ipod through the effect and turn the volume way up I can actually hear it come through, but when the effect is turned off it is a LOT louder.  Also the pot only appears to make a slight difference at the end of the cycle.  I'm sure it's something obvious but you know how these things are!  I'll post voltages later when I get in from work but I wondered if anyone had any ideas in the meantime?

[waltk]

Check your power supply first.  Is D4 passing almost 9V through to R5? (Did you use a 1N270 for D4, and leave the other diodes un-populated?)

You're sure D4, or the IC isn't backwards?

After that, you'll have to trace the signal.

[MikeH]

Hard to say, but when this happens to me it usually because there a solder bridge grounding the signal path.  Honestly it could be anything.  Do that whole "Debugging: what to do" dance and you'll figure it out.