@kitor: ok thanks for the precision! So I tried to get the ROM dumps, and they run fine in qemu (thanks names_are_hard!). So I guess it's a hardware issue...
I tried to open the LCD case+the pivot axis case, but I can't find any obvious broken wire... So I'm not sure yet if I should buy a new LCD screen (~30€ I think): I heard that LCD backlight can be broken due to a fuse on the mother board (and therefore changing the LCD screen would not solve the problem). But this is maybe out of the scope of this thread, so I created a new one there https://www.magiclantern.fm/forum/index.php?topic=26204.0 .
I tried to open the LCD case+the pivot axis case, but I can't find any obvious broken wire... So I'm not sure yet if I should buy a new LCD screen (~30€ I think): I heard that LCD backlight can be broken due to a fuse on the mother board (and therefore changing the LCD screen would not solve the problem). But this is maybe out of the scope of this thread, so I created a new one there https://www.magiclantern.fm/forum/index.php?topic=26204.0 .