1963 RCA CTC-15 roundie

[etype2]

Acquired a CTC-15 from a VK member here. It's in great shape and produces a nice color image.

Two questions:

1. After about 3 hours of operation, the color fades out to near nothing with a green tint. This does not happen gradually, it will be fine and then just loose the color all at once. Cannot bring back the color by switching the channel selector, fine tuning etc. After maybe 5 or 6 hours, if I turn on the set, it will be fine with great color image again. What should I check first?

2. The set is 100% original, so only plan to show it to guests that visit and watch vintage TV shows on DVD. What is best, leave the set plugged in or unplugged? Is there a trickle current in the set when plugged in?