I9 have a 20" panasonic tv when it is plugged in it doesnt turn on

Try below and if still doesnt work itsbetter to call a repairman .
Here is the simple 5 step process we follow when this happens to our plasma tv. It works most of the time.
1) Completely unplug EVERYTHING connected to the tv, including HDMI cables
2) Press and hold the power button on the tv for 10 seconds
3) Plug power cord ONLY back in to TV
4) Turn tv on.
5) Plug in all other cables at this time.
It is helpful to use a good surge protector with this tv. It still goes out occasionally but not as much.
If the process does not work, wait longer (like an hour) after unplugging everything

maybe try turning off at wall rebooting device can harm the computer if you turn off both you may turn off modem box thingie

You have a problem in the High Voltage section of your TV. I would call the nearest tech.

the blinking power indicator is actually a error code. How many times does it blink as I can assist you if you let me know how many times the led blinks

If the power led blinks its an error code such as 3 blinks means convergence failure which is the most common error for your model.Let me know the error code and I will assist you with what you need to do.

Can you post how many blinks the power indicator is blinking as that is an error code such as 3 blinks means Convergence circuits.

A friend of mine had the same prob after putting in brand new batteries, it was i bit wierd but i tried some different batteries and it started working , try some new batteries. hope this helps.

I need full details to assist you.Please let me know what is your cable box company?Which HDMI input from the TV?
Where do you set your cable box?Above?Below?Away?
Solutiondoct

my tv work in 5min. and shut off it self

Possible blown fuse or worse. If you attempt to change the fuse use the same amps that is in it.