Glad it worked! I was thinking along these same lines but would have never guessed the right order of the plugs without opening my CPU box. Good help from S&X - they're keepers!
Good luck in getting the rest to work! (And now I understand your message about the blank screen. It is normal when updating the OS, because the program waits for input from the console, but it'll never work - neither the message on VFD nor the keypress on the desk itself - with the COM ports swapped. It is only normal for OS update, in normal operations it would indicate a VGA card problem.)