Hi, I have an Hitachi 42PD9700 plasma TV. When the TV is off you can see a mottled/patchy area on the top right hand side of the screen (this is still visible when the TV is on if you look closely). This has increased slowly in size and now covers approx 1/4 of the screen. The mottled area is behind the screen. Any ideas?

SOURCE: Hitachi 42PD9700 Plasma TV about 4 1/2 years old -

The line you are referring to is definitely a capacitor problem. One or more capacitors on either of the boards are slightly bulged and is the cause for the abmormal panel voltages. I know this for sure because I have recently fixed a similar problem. Open up the back of the cover and look for caps that look like this on the boards marked x-main and y-main
http://www.wheresmydrink.com/wp-content/gallery/may-2009/capci.jpg
The slight bulging will usually be very hard to notice unless you look at the boards from the side. Let me know what you found so that I can help you replace the faulty ones.