Can anyone give me a definative answer on what causes these so called "dirty Patches" which are visible when the screen pans. After many hours of searching I have come to the conclusion that the shadowmask is involved in some way and degaussing either automatically through the tv's own circuitry or manually does nothing to help with this problem. It seems that many makes of Large screen crt's have this fault to a greater or lesser degree. Is there anything that can remove or lessen the effect???