My tv keeps going off at every 30 minutes where is the timer,it also blackout

defective timer. get a new one.

probably heating element, select a 90deg wash and see if the door glass is hot after 30 minutes

Try turning off the circuit for a minute, then set timer again.
Often a little picture/icon of a "baking tray with heat" when timer is passing power on to the thermostat.
Also, those timers fail often enough, is the oven brand new (or recent blackout)?

You posted under Paragon 2606 Panel-mount countdown timer.
If this is not your timer, add a comment.
http://waterheatertimer.org/Paragon-timers-and-manuals.html

2600 series is mechanical interval timer.
26006-00 can handle 10 amp loads.

Interval timer is a countdown timer that keeps Load turned on for set amount of time.
You set the time by rotating dial

To start timer, Rotate dial from 1 minute to 30 minute.
Rotating dial turns on Load and begins countdown.
Timer turns OFF Load after set amount of time expires.

lamp timer may need to be reset, or lamp door may be open. unplug tv for 1 minute, plug in and wait 30 seconds before powering on. make sure lamp is all the way in and door closed before you plug it in. if it keeps erroring, check the manual and see what the error code indicates

It is possible that your TV has a sleep timer and is so, it may be set to 30 minutes, check your remote control to see if there is a timer button If so press it and set it to 00

In the menu turn off sleep timer.

It is probable you have a poor soldered connection on the power supply board, hence the erratic timing of the TV going on & off. If you are competent with a soldering iron look for dry jointed soldering on the board. If not have a service engineer take a look at it for you.

go under you menu controls go to sleep timer and set it to off. if your tv control has a sleep button on it just press it until it say sleep timer off.

check your sleep timer settings. they stay on no matter how much you turn your unit on and off.