Whilst watching a TV signal from the Sony RHX 900 tuner the picture dims everytime subtitles are displayed. This doesn't happen if I switch to watching direct from the TV's tuner (the RF cable is looped through the recorder.) The aerial reception is a bit noisy. Also, while watching ordinary programmes the picture sometimes dims and brightens. Do I have a faulty tuner in the Sony recorder? I've noticed this dimming effect when titles are displayed in cheap TV's before, usually in hotel rooms, so maybe it's the tuner. Anyone come across this effect before?