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If you have left the machine unplugged for a few minutes, disconnected all but the power cable and then tried to turn it back on, and get the same fault, this would suggest a power board failure within the TV itself.
The next step is to confirm the make and model of the TV, and your postcode, so I can recommend a suitable service centre where you can get the TV repaired.
A typical repair would cost around £150. So it rather depends on the make and model of TV, if your not to bothered in terms of brand, you can pick a new 43" from Tesco at the minute for under £200 here.
Please let let me know if I can be of any further assistance, and appreciate if you can rate the service at your earliest convenience.