"Roy Page" wrote in
k.net:

I had a "mike stuck open" problem on my 1977 Piper Archer.
The PTT switch tests out fine and seems that the KMA20 audio panel is
the culprit.
I worked all the front panel switches many times and the problem has
gone away for the moment.
The mike unstuck as I was working the Marker Hi Lo switch [Extreme
right] I can't locate a either a user manual or maintenance manual.
Can any one help with suggestions on obtaining a circuit diagram so
that I can trouble shoot the electronics.
Also any tips on using and fault finding the KMA20 would be
appreciated.

Hmmm... Could be, but not likely.

First off, pull the KMA20 and push it back in (a time or two). Won't hurt
anything, and you never know. I am still suspecting a mechanical problem
in the wiring somewhere. UNPLUG the handheld microphone. The PTT on the
mike is wired in parallel with your other PTT, and the swinging mike cable
has a habit of wearing through the insulation internal, right at the plug.

I'm betting the problem is NOT the KMA20. [But I have been wrong once or
twice in my life. G]

jmk