Goodmans LD2650HD flat LCD tv. Around 12 months old (just out of warranty typical eh) for some reason one day screen just switched on with only the lower right quarter of the screen working. Still shows picture in this quarter and you can see faint outlines in other areas of the screen. Speakers intact and work fine, have full dialogue of programmes.
I have had electrical and electronic training and experience but know nothing about these tvs. Has anyone encountered this fault or know where I can get some good info on how exactly these lcd tvs work.
Thanks

Ian, February 2008

On an LCD display there are flourescent backlights to shine through the lcd to make the light. These backlights have a very hard-working part called the inverter. The inverter is similar to the ballast of a light fixture, except it's all done with small scale components, which run very hot and don't live very long.

I've fixed many LCD computer displays and laptop screens which had failed backlight invertors, which are typically a small separate circuit board. For example, a Compaq 20" LCD computer display, the board is approx 2" x 8", heavily protected with clear plastic, and has those blackish marks you see on a part that runs very hot.

I have not repaired a LCD TV, but I would suspect that they have multiple inverters due to the area of the screen.

My guess would be that either the connection to your backlight invertor has failed, more than one invertor has failed, or the power supply feeding these parts has lost it. Note that the invertor converts typically ~12V or so to around ~30KV, so approach with caution.

Tesla, February 2008