My tv turns of every 20 minutes for 30 seconds

This is a common problem with this set evidently, the problem is either in the back lamp of the set or the power supply. I have the same problem with the set that I'm working on now. This set has a 30 second on time and a 30 second off time and when it comes back on the picture quality is great. When I find out what the problem is, I'll tell you about my findings.