Mitsubishi cs-27tx1. Only has a thin horizontal line thru middle of screen
Total Vertical Sweep failure had occured in your TV. That is there is only horizontal sweep there, and the whole picture sweeps horizontally and you see a horizontal nice line across the screen, at the middle of it. In this case, all other buttons will work, and sound output will be Ok.
This fault is normally due to Vertical Sweep Out Ic trouble. You have to open the back cover of your TV, and have to pull the main board out. Locate the Vertical Output Ic. It is easy to locate it. There will be four wires going to the deflection yoke assembly [the coil fitted alongwith the picture tubes' neck]. Amoung them, two will be thick, and is carrying horizontal sweep signals. The other two wire are comming from vertical sweep section. Follow the wires and find out from where it comes from the main board. Somewhere near it orginates from the main board, you will see an Ic usually screwed into a heat sink [ a metal plate or so]; and it is vertical output Ic.
Check first, whether there is input voltage [working voltage] come to it or not. Sometimes an open resistor problem may occur to show this fault. Normally vertical section will have a voltage rating between 18 to 35VDC. If that voltage is there, surely the Ic said above is damaged. Screw it out and desolder it from the mainboard, and go for an identical type and number, replacing it will solve your problem.
Take all precautions when we works with an elctrical equipment. Keep away children and never allow even stand beside you while you are working, and let an adult beside you as a precaution. Never use metal chair. Do wear a plastic of rubber shoes. If can, keep matted the floor also with carpet. Ok
Wish you success.