[ICOM] IC-448A: No T/R Keying

[D C *Mac* Macdonald]

I recently bought one of these fairly rare oldies
to pair with an IC-228H or IC-228A (I have both).

When I received it, I set up my service monitor
to check it out.  Receive is fine with good S+N/N.

Radio will  NOT  go into transmit mode.  I have
checked it with three Icom mics that work on
all my other Icom rigs.

Does anybody have any simple suggestions as
to where to look for the problem.  I haven't
yet opened it up to look for a broken wire at
the mic socket, just so that you know that I
have thought of that.

TIA (thanks in advance) for any suggestions.

73 - Mac, K2GKK/5