Can I use a video switch box to use one monitor with several Amigas, and put an external scandoubler/flickerfixer after the switch to allow a svga monitor on all? Will it lead to any genlock sync issues, as some of these will be toaster/flyers or have external genlocks attached?
Obviously, you can't scan-double a signal twice. That'll cause you massive problems. If you had a scan-doubler that recognized a 30khz+ signal and didn't double it, you might be able to get away with this configuration.
Now, if you were providing 2 15khz signals into a switcher, with a scandoubler on the output, I'd think this configuration may work. It may depend on what type of switch you are using, though. Some higher-end KVM switches try to clean up or boost the signal a bit, and those might have some problems with a 15khz signal. A basic dumb switch that just passes all pins without touching the signal should work fine, though. Simpler may be better, in this case.
If all else fails can I add a scandoubler/ff on each and use one monitor on all without any sync problems?
This configuration will certainly work. It's what I use with a Belkin Omni-Cube KVM. :-) No problems. (With the Mr Hardware keyboard and mouse adaptors for each Amiga, it can switch PS/2 style keyboard and mouse, as well as the video.
