I built one of your kits, but get no sound from it when it's engaged.

We recommend re-tracing each step of the assembly process using the instructions. This will allow you to insure there are no wiring errors and check the proper orientation of the transistors, diodes and polarized capacitors. The next step would be to make sure there are no unintended shorts and cold solder joints. Cold solder joints are more common when using lead-free solder as many soldering irons don't get hot enough to properly melt lead-free solder.