The computer doesn´t show image when I try to run some demos, while the audio runs perfect (if the machine don´t hang up).
Have you tested these same demos on another machine, and seen them work fine?
It may not be related, but I noticed after I switched my A1200 from an '020 with 8Mb fast to an '030 with 4Mb fast that not only did a lot of my old demos run smoother, I also was able to see a lot of additional frames of animation and still pictures that previously were getting dropped. Note that this isn't a typo - I went from 8Mb fast to 4Mb, but it was the faster processor that made all the difference.
Perhaps the demos you're trying to watch require a faster processor?
FYI, I too have a PAL Amiga. Every dog-gone time I turn it on, if I want everything to run normally (other than demos or old games, for which I keep it in PAL mode), I've got to change it to NTSC mode in the early startup control.
Good luck,
Mike
