(see if you can determine if the clicking ciruit breaker is in the TV charge line or the line to the electric jack, before taking the advice below)
I believe you're hearing an auto-resetting circuit breaker. In early 70s trailers, that breaker is in the TV charge line, eg, the line that will recharge the trailer battery from the TV. I'm not sure what the design parameters were, but I surmise that it was intended to charge the battery while towing, so the current load limit probably assumed that that line would be powered when everything else in the trailer is off (moving down the road) and then not powered when you begin using lights and other 12V
systems (parked and tow vehicle is off).
If your TV wiring doesn't turn off power to that line when the engine is off, you'll deplete the TV battery pretty quick. You may find you don't have a problem [with the trailer electrics] by simply disconnecting the TV.