Here's a new one: STEC-60 attached to an Autocontrol IIIb. It's worked fine since I got the airplane, except for the pressure transducer failure I posted about here before. When I was headed to KNEW the other day, the PSS wouldn't do anything... in TEST mode, all the annunciators would light, but in ON mode, I got no panel lights and no response to any button presses. The POH doesn't contain any useful troubleshooting guidance and I don't have a copy of the installation manual. Any idea what I might check to see what's going on before I take it to the shop?