[RTTY] need some help with mtty

[john]

runing mtty version 1.65 b via bux into compaq computer window 98.
 rig is kwd 850 and I have preciously run mtty and writelog through this 
set up ok,,
this is at my farm station and have not run mtty for a while.
the problem is that in transmit , the rig will key, but all I get is a 
solid tone through the monitor-I do get power out
I can copy rtty ok, and the 850 is set on fsk position.
menu 11 of the 850 is set for on(mark)
bux green plug  in computer mic jack
bux white plug in computer skr/earphone jack
xmt panal of mtty  shows:  tx  uos,  txbpx    pt com1, which is the only 
port that will even key this.
misc panal shows  com txd(fsk)  usb port
I know it is probably something simple but for the life of me I can not 
figger it out..
any help would be very much appreciated..thanks
73 john