I had my old Narco COM 120 replaced with a new Garmin SL40 and now
when the new radio is turned on my intercom volume drops by at least
half. Anyone seen this before? It has the avionics shop baffled. I
have an SPA 4000 intercom and a King KA-134 audio panel. I looked on
the Bendix website and I see a notice in their manual's list for a
"blocking diode for audio muting" installation but I can't get the
manual without a dealer login. I wonder if that has any relevance.
Anyone come across this before?

Steve
KDMW
PA28-151