Questions about Yaesu CAT interface with CT

[zf8bs at twg.com]

I have a new Yaesu FT990 I have just started playing with and have run into
a wall trying to get it to work with the CT (version 8.52) radio interface.
If you have any experience with this, please take a look at my situation
here (see below) and let me know what you see that I'm doing wrong.  Any
suggestions would be very warmly appreciated!

The interface I'm using is a hombrew level shifter which uses the
MAX232 chip.  I built this about a year ago from the circuit given in
the February '93 issue of QST.  Initially, I built it to interface to
an Icom.  But the only difference between the Icom interface and the
Yaesu interface is that the TxD and RxD lines are brought out separately
to the Yaesu, whereas in the Icom interface they are OR'd together before
being fed to the Icom C-IV bus.  With the interface I have, if I OR the
two lines and feed them to my IC-761, it works fine.  So I know the level 
shifter is working correctly.  I split the TxD and RxD lines apart and 
am feeding TxD from the level shifter to the SI input on the Yaesu CAT
connector; the RxD on the level shifter is wired to the CAT SO line.

I am running CT version 8.52.  I have started COMTSR1 at 4800 baud and
have the "radio" interface in CT set to 4800 baud.  When I start CT,
I soon get a message that says "YAESU radio timeout".  About a second
later, I get a second message that says "YAESU radio timeout 0".
If I type a frequency into the logging line on CT and hit "enter",
the CAT light on the Yaesu will flash immediately for a half second or 
so, then nothing happens for about 5 seconds.  At that point, the 
frequency of the 990 will change to the one I entered.  (On my Icom
the frequency change is virtually instantaneous, so I know this isn't
the way it is supposed to work.)  I am not able to log any contacts.
When I try, I get the two timeout messages (above) and see the CAT
light flashing on the FT990, but nothing gets logged.

Unless anybody sees something they recognize here I'm going to have to go
take lessons in operating a line analyzer.  I know that would be good for
the soul, but I'd sure appreciate a short-cut to success!  I put the same
basic message on my local packet cluster and got back a response from one
person, W6YA.  He said he had the same experience using the Yaesu level
shifter he bought when he hooked it up to his FT-1000.  He gave up on it,
and wants me to tell him what I learn.  Please don't tell me this is a 
generic problem with CT!  I can't live without my radio interface to CT!!
                                            de Bruce/AA6KX