[R-390] Testing Collins Mechanical filters:

[Tim Shoppa]

KIORQ writes:
> But the audio is not very loud.
> Anyone have any ideas?

Ohmmeter tests:

Across input and output coils of each filter, it should
be 50 to 100 ohms. (Web says 50 to 60 ohms, my
memory says closer to 100 ohms...). This is the
DC resistance of the transducer coil.

Between the signal pins and can should be
very very high resistance, bigger than megohms.
If it's leaky at the megohm level AGC action will
reduce the gain.

If there is leakage but only between one end and
ground, it may be possible to isolate the filter can
from ground.

Standard reference on rebuilding filters: http://www.delphelectronics.co.uk/filter390a/ 

I kinda wish that I would get laid off of my job
so that I could have time to fix my bad mechanical filters
(and all the other old radios laying about the shack.)
As it is others are getting laid off and I have to work extra
hard to pick up the slack.

Tim N3QE