Need Help with Mitsu ws- 55511 will not stay on

I have a Mitsubishi WS-55511 model that turns on, then turns off within 2-3 seconds. I have read alot of post's on the net about this problem, but I dont know how to check certain componets that I need to. I have the v21 service manual for it, but it does not tell you how to diag. I do have an error code of #23. I have checked every fuse and all are good. I have already replaced the capacitors in the DM but no help. I did get the TV to work for about a month by turning down the gain dials, then it would power on and stay on, then I had to adust the color, sharpness, etc with the gain dials. If I turned the gain dials up too much, it would turn the TV off. Now its not turning on even when I have the gain dials all the way down, system reset worked once or twice, but now if does not help at all. Like I said, every fuse listed is good. I need some help to diag what componet is at fault. I am an auto tech and have hands on, I can solder, and I have time and patinence to do it. Please help