That's a clear indication that you have a bad power supply in your TV.
you know how to DiY...I suggest you open your TV. Locate the power
supply section, it is where the end of the power plug is connected.
Replace all blown or bulge or leaked capacitors with same value. That
will fix your TV problem.
The hardest part is to disassembling your TV cover, cause you will need to pry off the snap in lock at the edge of your TV.
Power supply board should look like this. Examine the capacitors in the board
After replacing blown capacitors...it should work again.
Things you will need.
1. A plastic flat end screw or any object with flat ends....to fry off the cover
2. Soldering iron.
3. Soldering lead
4. Soldering pump.
5. Flat and Philip Screw
6. Replacement capacitors (of same value with the blown one) that you can buy to any electronics store.
Hope it helps