Mine powers up and allows the pilot to xmit. It will not allow the passenger to xmit. We verified that the signal is getting to the DRE with an O-scope. I borrowed a friends DRE and plugged it into my harness and his worked fine with my installation. To further complicate the diagnosis, my SL-40 was also dead on arrival right out of the box. It would not modulate voice, but would lock a carrier wave. Stark Avionics sent me a new one, much to their credit. What are the odds of both the intercom and radio being faulty brand new? I hope that I have used up all of my bad luck with these two issues...they have cost me much wasted time, but I have learned much about diagnostics along the way. I am much more confident with electronics having gone through this process...
Don