I set up a end fed antenna for my 7300, Palomar 9:1, 4:1 unun. 67 feet of wire. The antenna worked fantastic for at least 6-8 months. Now on 40 meters it trips my GFI outlet that the power supply is plugged into. Only on 40, not 20, or 80. Do you think the unun is bad? It may have gotten moisture inside, but there is no visible damage inside. help!