I have a Quintrix F inside my TV (a Philips) and it has problems with color purity. The picture is yellowish in the bottom right half and the corners are a bit dark. It seem to vary depending with the temperature of the shadow mask. If I watch 4:3 material for a while, when I switch to 16:9, I get the impression it's worse. If I watch 16:9 material for a while, the color purity seems to get better, but not good. Before getting this set I had another Philips, which had a Philips Cybertube and had no problems whatsoever with color purity, so I don't think it's a problem with external magnetic fields. It might be related to the higher dot pitch of the Quintrix F over the Cybertube (0.66mm vs. 0.7mm) making the shadow mask softer. I'm not sure if it's supposed to be like this though, does anyone with a TAU recognize this problem?