Black horizontal lines across entire screen.

To clarify, are the 3 black lines horizontal (left to right across entire width of screen)? or are the 3 black lines vertical (top to bottom across entire height of screen)?

Horizontal lines are almost always the result of a failed panel, and no board replacement will fix the issue.

Vertical lines such as you have described (only 3) are probably also a bad panel. If the black lines were evenly spaced in a repeating pattern, it could be a mainboard or TCONN board.

Has this panel been cracked? or perhaps cleaned recently with too much water or cleaning solvent that has gotten the screen wet?

You may have to sell the TV for parts.

hello

It sounds that the main power supply section to your TV has the fault. The horizontal thik lines that appears crawling down across the screen should be of video 'HUM'. Have you replaced the main filter capacitor at the power supply section? If not, replace it along with the main rectifier. The AC power is rectifed by a bridge and applied ot this main filter capcitor. It will have a capacitance value between 120 to 350MFD 450VDC. Check this section. Measure the rectifed DC voltage acorss this main filter capacitor. It should be around 350VDC, if your home power supply line is 220VAC. If it is 110AC, this DC voltage will be around 165VDC; and it should be. If rectified DC voltage found lower than the input AC voltage, replace the rectifier bridge. In some sets, this bridge section have four diodes. Some other circuits, a bridge rectifier stalk may be used.

this occurs very commonly in all LCD monitors... this is because each and every cells in the LCD monitor are energized by the vertical and horizontal electric fields placed around the frame of the monitor... if a particular field does not gives the power to the associated cells to it, then the entire line of cells will not operate and together they looks like a single line...This is what happened in your case...


have a look at my tips for replacing the LCD screens on monitors, by clicking here....

The line is there because the vertical deflection unit - the one that spreads that line across the entire screen to form the image - has failed. Replacing it is a job for a professional, or at least an experienced amateur, and the parts will be quite difficult to find for such an old tv . 

you can try contacting Lumaco they are a British monitor repair specialist.
www.lumaco.co.uk

It might even be cheaper to buy a new one.

It looks like you've got problems with your screen. If that one is on a warranty, replace it

A line on an LCD, either horizontal or vertical usually means the video driver board is defective or the screen is defective, does it show up as black even on a dark screen? That means a line of LCD "shutter"s is not working and there is a problem that cant be fixed by a reboot or channel change. Bummer.

Sounds like an inverter problem. If the power supply is internal replace the capacitors coming out of the voltage regulators. These are usually 1000mf and/or 470mf. If that doesn't do the trick look up the numbers on the 8-pin chips that drive the secondary transformers on the inverter to see if they are getting the right voltages.
Good Luck!

Yes. There is no vertical deflection. The circuit that controls vertical deflection is bad. This is an easy fix for a TV tech. Take it to the TV repair shop.