Yes,but I have the problem described when connected via composite video-out too.
Oh. Yeah, that's probably a problem on the motherboard. Clean up and replace the capacitor if you can. If not, time to ring up a repair shop.
From what I remember reading, Amiga.fr (which no longer resides at that address, but is still around; check links page) does Amiga repairs, as does
Mr. Hardware in New York.