[RTTY] 756p2, rigblaster pro, mmtty

[Ian]

I have an IC-756Pro2 and a Rigblaster Pro and can't seem to transmit FSK.
I'm pretty sure all the cabling is correct. Rig control through CI-V is no
problem.  I can decode RTTY just fine in MMTTY on my laptop.  The laptop has
one serial and one USB port so I use a USB-serial converter that sets up as
COM5 and use that on the Serial-A of the RBPro.  The real serial port (COM2)
goes to the RBPro Serial-B for FSK control.  Also have the WMR cable that
plugs into ACC1 and provides level audio and FSK control. Been through the
MMTTY help and AA5AU's web site but I'm missing something.  Any ideas?

Many thanks & 73,
Ian N8IK