hi,
Check out QST, go back a few issues and
there was a hint/kink story I believe
on a mod to the mike.
Basicly you remove the foam pads inside the
mike and add a small setscrew to the plastic
ptt arm. That will give you a firm button
press. Be sure to replace the spring.
FYI, my 742ad had mike problems, even if I put
a brick on it it would not key up radio.
SO, some alcohol on a qtip and I cleaned out
the ptt switch on the mike board.
Now it works non stop !!
73