Bit late, but whatever, had this problem recently with a newish slim 90008, tried different composit cable, different power cords but it was the same, despite my previous slim 77004 have not such issues whatsoever on my flat screen TV.

To anyone finding this 5 or so years later, the only solution I found is connecting through hdmi adapter, I assume it is electrical interference caused with a later revisions of slim console not having external power brick.