Bendix King KMA20 - Stuck mike open.

[Roy Page]

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.

Thanks guys.

Roy Page
Beloit, OH 44609

[John_F]

Look for wires that run tightly across sharp metal surfaces.
Look for signs of water causing corrosion.
Make sure that the mic plug is fully inserted.

On Tue, 12 Oct 2004 00:52:54 GMT, "Roy Page" >
wrote:

>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.
>
>Thanks guys.
>
>Roy Page
>Beloit, OH 44609
>

[James M. Knox]

"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