Hi Laura,
I’ve had my EC-3 for a few years and had several problems. The first 2 were cable failures. I tried to use an aftermarket 100′-0″ and the ends were not to spec. If you have a cable from Pana and it has a (unusable) BNC on the end, most likely it has failed because of useage or 1 or more of your pins has failed. When you send in the unit for service, send in the cable.
good luck
M