Sony Trinitron won't power up

It is a video output section problem. Check all the voltages at this section circuit.

Check for bad connections on voltage regulator ic, or bad voltage reg ic in power supply.

my Sony trinitron kv-g21s2 TV not working . conned to the power blink in TV power indicator led

the red wire on the top of the tube will be connected to l.o.t ..inthat lot u can find g2 below screw....& focus upper screw...

Sony Televisions have indicators like blinking lights to give you a clue what parts have failed.
In your case it could be the worst your picture tube.
Do you remember how it normally would start (blinks) and if it was lacking ant color in the picture or if it just wasn't really clear any more?
10 years was a good life without any service.

it should be in menu

Trires unplug,replug about an hour later see if it reset it self.Not take to the shop the two power ICs help the power it dead.Need it replaced.

The vertical output IC has failed/Power to the vertical IC is out/ or there is bad solder on the pins of the vertical output IC.

the problem there is a loose connection on the board,you said that you smacked the right side of the tv and it goes normal.there are parts that should be resolder on the board in order to back into normal operation.

there are two possible defects in your circuit. 

However, if the led blinks for about 10 times your tuner is defective 90%. 

You will need a scope to check or you will need to take it in for service.