My tv is about 3-4 yrs old. Toshiba Regza 47 inch. The tv has been on all day and suddenly a faint grey line appears on the right side of tv only noticeable when picture is light in colors, cannot see if colors are dark?

Hi,
You have to check the back light section of your lcd tv. All lcd tvs have back light to illuminate the pixels. Two types of back lighting are there CCFL (cold cathode fluorescent Lamp) and LED. In your tv its CCFL. CCFL need high voltage 1000V or above . For providing this high voltage there is inverter stage ( back light inverter). Also there will be 12 or more CCFL behind the lcd screen. If any on of there CCFL failed the there will come a gray bar noticeable only when there is hight light.

There will be two causes for this problem.
1. CCFL is faulty.
2. The inverter transformer driving CCFL is faulty.

You have to check the inverter fist. For conforming which one is faulty do the following.
There is 10 independent connection for every two CCFL from the inverter board. Try interchange the two nearest connection. And watch is the line is shifting or not after every interconnection. You have to try by interchanging all the nearest to connections for CCFL.

If the line shifted then the inverter board is faulty. If the line stays there then the CCFL is faulty. Normally there will be problem with inverter transformer. If the transformer is faulty then you have to replace the inverter board as a whole.
ok