Rheostat Audio Interference

In article ,
Jonathan Goodish wrote:
There is a terminal block under the panel to which it appears some of
the avionics is grounded, including my intercom. When I pulled the
intercom ground off of this terminal block and grounded it to the
airframe, even near to the block, the problem disappeared and I regained
normal intercom operation with the radio lights on full bright and no
noise in the intercom. I now wonder if the terminal block is grounded
to the airframe, or what is going on there. Would it be typical for a
terminal block to be anything OTHER than a ground? I didn't have
anything with me to measure voltage on this block or check for
continuity with ground.


I am wondering if this terminal block could be the radio light bus
instead of ground. It seems like an odd location, but I have no
expertise with avionics installations so I don't know what is common and
what is not. It would seem logical based on the symptoms and
resolution. I will have to check it with a meter tomorrow.



JKG