Dark video out with wrong aspect ratio - Help!

[raerek]

I've bought a Sizif 512 E1 from sellmyretro.co.uk in 2023 - and unfortunately I have only time to try it now:).

The image is

• dark and
• wrong aspect ratio
  .

See https://1drv.ms/i/s!Aq2QBO3N4DCVgnScRnvyvh0E6aQM?e=YThGSy
That is a CIRCLE 50,50,30, so it is supposed to be a real circle:)
Found the menu item for brightness boos. It did make the picture brighter but it is still gray instead of white.
I've tried with two different LCD TVs, both old, with 4:3 screens - same result on both.

Sizif was shipped with J6 pins 2 and 3 connected. I've read that connecting pins 1-2 and 3-4 might help, but it dd not.

The Sega cable is form here.

Thanks to anyone being able to help.