I have heard that this fault (overheating) is common in Sony TVs but I don´t know in Mitsubishi.
Probably there is a trouble on power supply board.....usually bad capacitor
It is not advised to fix power supplies of gadgets because they can cause shock. I would recommend you check with a technician for help.You can call a local TV repair service, here you are a tech website www.tvrepairjacksonvillefl.com
henry, October 2012