Spoiler
https://www.retrorgb.com/rgbvideocard.html - AGP & PCI solutions – Compatible card + Soft15Khz
this should work (as Guspaz said the monitor needs to be set the RGB though for the colors to be right).Tried UMSA (Converts 15Khz RGBHV via a DSUB HD 15pin to 15Khz RGBS SCART signal.)
So, I installed Catalyst 4.3 and Powerstrip 3.30, added a custom 320x240p resolution, and it worked on my monochrome IBM 8503 monitor that seems to support 15kHz, BUT not with TV or PVM. There is no signal on the TV, and the very same dark, distorted, greenish image in RGB mode on the Sony PVM, I've connected an external sync, of course. Yes, I'm ignorant, and I don't have a deep understanding of video signals and CRT, but I think my first priority is to understand why there are no colors!Soft15Khz can be used as a simple free alternative to Powerstrip...