I have a King kt78tso which was working prior to nav/coms replacement. the transponder is illuminated but non fuctional to radar. I traced the wiring harness out of the transponder and found an "unattached wire" labled "phono out". I am not certain of how this relates (if at all) to the output of my transponder, but its the only visable disconnection.  does anyone have any thoughts on this or had a similar non fuctional transponder?  Thank you for your responses in advance.....