Philco Predicta 9L37 chassis horizontal output tube red plating.

[Dangler]

I've had this sitting around for about 15 years and decided to get it going. I recapped the power supply first as a precaution. I plugged it into a variac and slowly brought up the voltage until it had a full raster except for a small 3inch spot in the top right corner. With a vcr hooked up, it had a good picture and sound then I lost horizontal sweep with a vertical line in the center of the screen. I immediately unplugged it and noticed the 12DQ6B horizontal output tube was red plating. All of the tubes were replaced when I got it. It's covered in Sam's 439. I do have the Sam's. I've worked on solid state TV's for about 30 years but am not very experienced with tube sets. Anybody have some ideas about what might be causing the red platiing and loss of horizontal sweep? I have a Motorola VT-71 next in line as well as 3 others. Thank's in advance for any help. Dan.