If you have an Amiga RGB monitor (not SVGA), make sure the A4000T's monitor output is working, I'm not sure what these DB-9 or DIN connectors are that you speak of, my A4000T doesn't have them. Perhaps they're some video editing cards that aren't usable for the OS Workbench/desktop display?
If an Amiga monitor works this way, you should be good, and find out what the heck those other connectors are coming from. Once you know what card that is you can start finding out if you can use Cybergraphics or Picasso96 drivers with it to possibly run the OS display instead of through the A4000T's monitor output.
If the Amiga monitor don't work, you may need to reseat the A4000T's video riser card. I used to have a problem with that and/or the SCSI riser coming loose as they'r eboth on pin headers, and I eventually got sick of it wacking out every time the tide came and went and used some hot glue to hold them in place better. I always hated PCs that used hot glue and I wanted to change something, but my A4000T really needed it! (Now I build my own PCs instead of taking on old hand-me-downs from crazy older manufacturers)
