Dust conducts electricity, so try blowing all dust out of the unit. Camel hair brushes don't conduct static, so if you can get one they are terrific for dusting electronics.
The Amiga 1200 has a circuit to detect if audio cables are attached, and will switch automatically between mono/stereo This may be the source of your screeching. Look for any solder points coming loose on the audio jacks. Make sure your left/right cables are the same length, too. Weird things happen with those kinds of automatic circuits.
NTSC/PAL power shouldn't matter, as everything is converted to DC current. But, I'm not 100% sure about this.
DONT use isopropyl alcohol, it can (and will sooner or later) destroy the lens.
Correct. Alcohol will disolve many kinds of plastics, rubbers, clearcoats, and powdercoat finishes. It should only be used to clean metal and glass unless you know it is chemically compatible with a surface.
Don't use CD cleaners, either. The bristles and cleaners used on many of the cheap ones will actually scratch the lens, as they are designed for players with glass lenses.
