I have an old KT79 transponder that began being intermittent in reporting altitude and finally stopped altogether during a flight Saturday. I had the biannual IFR certification done in April and had some issues after but would always clear after cycling power. It had done so prior to the calibration a couple of times as well. I plan a panel upgrade next year so don't want to replace right now. Any suggestions or has anyone had to address this before.
Don