I don't have any user manuals, but I have the service manual. According to that, the 1902 happens to be a combo Composite Video or Digital (CGA-type) RGBi monitor.
If you have a continuity tester handy, I'm sure you'll find that the cable you're using is tapping pins 3, 4, and 5 on the Ami's RGB port (that's the Analog RGB, which gives you the 4096 colors). What you need is the cable that'll use the Digital output pins of 6, 7, 8, and 9. Digital RGB will allow three bits (R-G-B) for color, and a fourth bit to turn on/off the Intensity (i), giving you 16 colors. Actually, now that I think about it, this is more akin to the old "Tandy" graphics, as CGA only gave you four, and EGA had higher resolution.
If you are handy enough to make your own cable, then you'd wire it up as:
1902 8-pin DIN to DB23F
1 -> N/C
2 -> 9 (DRed)
3 -> 8 (DGrn)
4 -> 7 (DBlu)
5 -> 6 (Di)
6 -> 19 (Gnd)
7 -> 12 (VSync)
8 -> 11 (HSync)
(Horizontal and Vertical sync signals are combined internally of the 1902 to get a composite sync.)
Switches on the 1902 should be something like:
CVS/CVBS = Composite
LCA = Luma/Chroma/Audio (Split composite)
RGBi = Digital RGB
VCR = Switches in an extra comb filter for video playback
Green = Monochrome using green gun only
banzai
