I had one unit to quit working last night. So... I ruled out the following possible problems. Pic, Comm chip, fuses, data cable.
Here's what it's doing when going to test mode. The unit will attempt to go in test mode but the display output will not cycle in a typical fashion. Plus... none of the LED indicators on each channel will light up either. The 5v and 3V lights are on as well. It will retain its channel assignment.
Where would be a place to start to find the failed part? I'm out of ideas for now.