JohnM

I just wanted to follow up with the resolution to the issue. The shop swapped the RF cables on the radios (Comm 1 to Comm 2 antenna and vice versa) and the issue went away for a few months. Plane went in for an extensive avionics upgrade and the problem came back, this time not associated with PTT on the radios. Finally on a local flight CB tripped, and no power came back when CB was reset. Shop found that the field wire was loose/broken within the connector to the alternator, replaced the connector but now the alternator was not putting out any voltage. One new alternator later and all seems well, no CB trips or issues since the alternator was replaced about 40 hours ago.

I have a JPI 900 and have looked at the amps and volts when the events happen. There is no spike when the PTT is pressed, I agree it probably happens too fast for the engine monitor to pick up.

Good idea, I will give that a try.

The ACU was the first thing we started looking at, it was sent down to Don Maxwell for inspection and was told it was good to go. I got the plane in December and this issue showed up about 2 months ago. Maybe would happen once every 5 or so flights, I initially thought it was just random CB trips. It wasn't until recently that I realized it was happening on PTT presses. I have not done any panel work since I have had it. Before we sent the unit down to Don we were looking at Zeftronics but were having a difficult time finding a direct replacement for it. The splitter in the back is for the VOR and is hooked up.

I am having some strange issues with my Alt Field 1 circuit breaker that I am hoping someone can shed some light on. I have a 1989 J where 6 out of 10 times I use the PTT on Comm 1 (GTN 750) the Alt Field CB trips. This does not occur if I am using Comm 2 (Kx-165). As far as I can tell by the wiring diagram there is no connection between Comm 1 and the field circuit. The voltage regulator was tested and came back okay. The only thing I can think of is the RF cables from the Comm radios run across/near the voltage regulator wiring harness and that maybe there is some bleed over during transmission that is causing the field circuit to trip. Has anyone run into this issue before? I appreciate any help that can be provided.