RadioBanter - ACC2-connector on Kenwood TS2000 for RTTY with MicroKEYER

While trying to hook-up a MCP ( a MicroKEYER from MicroHAM) to the
TS2000, I discovered the MCP doesn't work while connected to the ACC2
connector on the radio.

I try to use the TS2000 with the MicroKEYER for RTTY-FSK.

My problem is this : on the pins 3&4 (= AF output + GND to connect to
the MCP for digital operations) is NO (audio)signal ! ,(only about
100mV DC) , this for ALL modes (FSK,CW, LSB , USB , AM) EXCEPT for FM.
In FM-mode there is on these pins a nice and proper audiosignal (!). (I
assure you I measured the signal on these pins with a scope and
listened with headphones.).

In the radio's MENU (n°50) I adjusted the audio level for max. (9).
It doesn't make any difference. I read carefully the manual, and I
think all the radio settings are correct.

This is very unclear for me , no audio for FSK/LSB where it is needed
most, and nice audio in FM when this isn't needed.

The solution I use momentary is using the speaker output of the radio
for RTTY operations. A disadvantage is that I have to use the radio's
main AF control to adjust the signal level in stead of the radio's
menu 50.

I really would like to use the ACC2-signal for RTTY-operations.

Is there something wrong with my radio, or do I something wrong ? I
would appreciate it very much if you could help me.
These are my radio menu settings:

FSK shift 170Hz
(menu 38)
FSK polarity :INVERSE (menu
39) necessary with MicroKEYER
FSK tone 2125Hz
(menu 40)
TNC Main and SUBband AF output : 9 (menu 50CD)
External TNC :MAIN Band (menu
50E)