On May 28, 1:36 pm, "RST Engineering" wrote:
Thanks for your suggestions. The COM 120 was wired to the COM 2 input
of the audio panel (KMA-134)

You really need to be quite specific when you make statements like this.
What lead/terminal/connection of the COM-120 was wired to which lead/... of
the audio panel? Audio panels will generally have two inputs, speaker and
phones. Each is terminated differently and are quite different
electrically. Was this the only connection between the COM 120 and the
audio panel or were the mic audio and key lines also connected? Did they do
an exact wire-for-wire swap or did they do some other mickey motion with the
new radio installation?

, and the audio panel output wired to the

SPA-4000.

Again, specifics please. Was the audio panel output wired to an input on
the intercom or were the two outputs paralleled?

I believe the shop just removed the COM 120 and wired the

SL40 in it's place, so it should still be the same. I haven't noticed
anything different or unusual, i.e. if I select COM 2 I only hear COM
2.

So how does "the shop" explain it? You paid good money for an installation
and you didn't get it. Can they explain it away to you?



I didn't check the intercom mode of the SL40. I'll do that.

That's a possiblity if the SL40's intercom is inverted in phase to the
intercom's output.

You say the intercom volume drops in half when you turn on the SL40. Is it
just turning on the power or do you have to have both transmit and receive
selected to the SL40 before the volume drop occurs?

Jim

Jim,
I haven't delved that deeply into the wiring (yet) because the shop
has told me that they will get me back on their schedule to bring it
in and they will make it right. They have a pretty good reputation, so
I'm not too worried yet (Penn Avionics at Brandywine airport near
Philly). If I hit a wall, I will pull out my multimeter and dive in
and make it right myself if I have to (and then never use that shop
again).

To answer your questions that I can answer right now...

They indicated that they did an exact wire-for-wire swap with the COM
120. The intercom volume drops as soon as you turn the SL40 on. You
don't have to be transmitting or receiving for the problem to occur.

Steve