All,
I have worked out a design based on JediMatt's work a few years ago to hook a Geneve 9640 to a VGA monitor using a GBS8200 video converter. I have added a couple of things to the circuit.
I am using it right now and connected to the BBS. It looks pretty damn good too. Sharp and all the colors seem to be accurate.
You can read more about it on AtariAge:
http://www.atariage.com/forums/topic/279117-gbsvga-genie-v10
I am planning a run of boards for 9640, AVPC and EVPC
--- Mystic BBS v1.12 A39 2018/04/21 (Windows/64)
* Origin: 9640 News BBS (80:774/27)
■ Synchronet ■ Freeway BBS, Bendigo Australia. freeway.apana.org.au