There was an article in QST within the past five years that
dealt with this problem and how to fix it - with cores and
caps at internal locations.

Bill Evans VE4UD
"N0DG" wrote in message
...
My MC-60 has bad RFI operating on 40 meters. I have done
the usual jumpering of
pins 7 & 8 (PTT gnd and mic gnd) but did not help. It
only shows up when I
touch a metal part on the mic. The best advice so far is
to wear rubber
surgical gloves to operate on 40. OH I did try the ferrite
on the coiled cord.
that did not help either.
What next?
Don N0DG