how can I repair a backlight on a technosonic lcd2018 television?

Obviously the problem is either power supply or inverter board. Check the feed from power supply which should either be 12 or 24 volts ( going by similar sets) If this is missing look at the capacitors which decouple the feed. They shoud be 1000 micro farad and working at 35V, If the set is 2 years old or more, they should be changed. They must have a temp range of 105degrees and not 85degrees.. If the feed is there then possibly one of the transformers...believe it or not, the inverter will run with duff txs but backlight will be dim...possibly your problem...otherwise change the inverter...........

Mike Johnson MJTV Coleford Glos..
February 2010

IT IS NOT ALWAYS THE INVERTOR PANEL THAT IS FAULTY,I HAVE HAD 2 TVS TO REPAIR RECENTLY WHERE ONE OF THE NEON BACKLIGHTS HAVE FAILED.
A REPAIR IS POSSIBLE BY REMOVING THE SCREEN PANEL AND DISMANTLING IT CAREFULLY TO REMOVE THE FAULTY TUBE,I KEEP A STOCK OF BROKEN SCREENS WITH GOOD BACKLIGHTS FOR SPARES AS IT IS DIFFICULT TO BUY THE TUBES ON THEIR OWN AND THEY ARE EXTREMELY EXPENSIVE.
ONCE THIS IS DONE THE TV WILL BE BACK WORKING AGAIN.
ANOTHER CAUSE OF NO BACKLIGHT CAN BE THE IC THAT DRIVES THE INVERTOR THIS IS ON THE MAIN TV PANEL AND THEY ARE USUALLY IMPOSSIBLE TO REMOVE WITHOUT SPECIALIST DESOLDERING EQUIPMENT.
HOPE THIS ANWER IS OF USE TO YOU.

PETER COPPING
February 2008

it is the inverter boards which drive the backlight, one of the transformers on the board has gone, if you can't measure which one and swap, you would be better to swap the full inverter board, some lcd panels have x 2 smaller inverter boards instead of one large one

del lcd & plasma engineer
February 2008