[Icom] SM-20 DESK MIC PROBLEMS-756 PRO

[David S McCallum]

Have developed a problem with my SM-20 Desk Mic. At first it starts to
work fine, good alc indication and shows rf power output and the scope
shows output. As I talk I noticed the ALC starts to bleed off and stops
at zero, my scope on the radio still show an output indication. If I
unkey and rekey it shows good ALC but then bleeds off again then I start
getting reports of breaking up, sounds of RF and when I'm speaking into
mic the reports say it sound like I am crunching some paper in front of
the mic.

I took the plug apart that goes to the radio all connections and solder
look ok,  jiggled all the cords on the mic and thought I had it isolated
to a bad wire but when I took it all apart everything looks ok and
continuity checks on the cables all looked good. I can also hear the
break up problem on the radio monitor system but not the crunchy paper
sound.
This just started a week ago and my hand mic that comes with the PRO is
working ok.....Any ideas gang and does the mic element cover unscrew so I
can check there? Thanks and hope some one can help, 73 Mac 

 
David S. McCallum/USAF Retired/ Chief Mac/w7sac/4