Our trusty KT 76 was really not that trusty. Some stations would pick up a signal but most would not see any response which was becoming just a bit embarassing. I had ordered a second hand KT 76A from Harry Mendelssohn not really realising the problems invoved in using this as a KT76 replacement. Our local avionics engineer obviously realised and was becoming elusive. The trays are just a bit different, the plugs are different and unfortunately the pins are just a bit different. The KT 76A is installed with the help of a soldering iron and working fine but will probably put a Trig mode S as the long term solution.