Hello [Sir/Ms], My name is XXXXX XXXXX XXXXX you for posting your question on Just Answer! I will be happy to help you with this problem,
Can I have your make and model? on the rear of the TV
First let me say sorry I don't have a quick fix for this problem.
The problem you are describing is a very common one in LCD sets like yours. The power supply circuit has failed and will require component replacement in order to get the set working again. This repair should be done by a qualified technician, these sets can be dangerous to someone who does not know where not to touch, also it is very easy to cause more bad than good if you don't know what you are doing. Also the use of a solder Iron very well will be required. I cannot stress enough, you must be able to solder very well or can cause many problems.
If you have solder equipment and would like to complete this repair yourself please let me know and I will give you instructions on how to complete this repair. Parts can cost you anywhere from 5-20 bucks depending on where you buy them at. But remember I have seen quite a few people destroy perfectly good sets by not knowing what they are doing so just take that as a caution.
A good repair shop will run you somewhere between $100-$200 to repair this for you.
If you would like any additional information or have more questions please don't hesitate to ask!
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