Having a bit time, I created a monitor adapter for my Siemens PCD-2.
The Siemens monochrome monitor has no own power supply, it gets its power by the DB9 connector (strange!), means +12V on pin #2.
I had to cut the connection between pin #2 from the mda/cga card and pin #2 from the monitor, and also had to get 12V from elsewhere. This is my solution:

Now I will hopefully be able to use also an EGA card (without 12V power supply) with my multifrequency monochrome monitor (this monitor model is *very* rare).

See original manual page of the Siemens PCD-2 at "related link" below.

See also my web page about the Siemens PCD-2 >here<.