AES without video output

When I turn on my AES, I see nothing but a black screen. Audio works, though.
I've tried it with different cables and TV sets, so I'm pretty sure it's a defect on the machine itself.
What could be the reason? Are there any possibilities to fix this up?

IT could be the cables????? or the port?

Worked fine on a friend's TV set. So I assume it's a compatibility issue with mine (and my brother's. and my father's...). Are there any possibilities to solve this by modding the cable?

Are you trying to play an NTSC system on a PAL only tv? Some newer tv's in Europe (when I moved from Spain) supported both NTSC and PAL signals. On the ones it works do they have newer televisions?

The AES is japanese, but my TV supports the NTSC signal. I got a japanese PS2, and it works fine.

I don't know how old my friend's TV is, but it LOOKS older than mine

The guy from whom I bought the system talked about having 2 scart ports on his TV, from which only one could be used for the system...