Definitely sounds like a short in the trailer wiring. Shouldn't matter whether TV is running or not, but make sure the lights are off when hooking up, so you don't throw a large sudden current spike on the fuse. With no current on the trailer wiring (not connected TV), remove a bulb and check with a continuity meter whether or not the hot terminal in base of socket is connected to ground. If so, either that individual hot wire is rubbing a ground somewhere, or perhaps your main turn sig wire in the 7-way is grounded. Either way, you will have to go through the system and find the short to fix the problem.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
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