replaced tcon board, worked for a few minutes but now no picture

My Sony TV stopped working. The red LED was blinking 5 times. So I replaced the T-CON board, and it started working again. But after 20 minutes or so, the screen went black. I turned the TV off and on again, and the picture came back, but only for a few seconds. Then the picture would come and go intermittently (the sound worked fine). Then, I tried it later and the red LED started blinking 5 times again. Any ideas?