I just posted a video of Andre's test ROM V2 running on my Flash System4 boards:
I just wanted to share the experience with all interested pin nerds around.
This ROM has more tests and is more precise in its diagnostics than the famous Leon's ROM.
It helped me debug the blanking signal: With Leon's test ROM the blanking signal didn't blink but the last test of Andre's ROM did make the blanking (and flipper relay) blink.
Very good debug tool for Williams System 3-7.