Mistsubishi vs-45605

 I have a Mitsubishi vs-45605, and I can turn it on and it will be fine until it warms up, and then it has horizontal lines going from top of the screen to the bottom. There is still a picture, but of course you cant watch it with the lines. I know this problem has probably been addressed already, but I can't find the "exact" fix for it. I heard I could put a fan on it, so I set a fan behind the tv to see if it would prevent/stop the lines, and it did. I just need to know what the problem is and where to look for the problem,and of course, how to fix it. I hope that helps, and any help would be appreciated. My email address is [email protected]