I have a full an hitachi l42v c04u full hd flat screen tv it has an on/off problem when switched on. blue on/off light flashes on/off/on/off all the time but no picture comes up on the screen

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. Viewing it in "Mosaic" or "Magazine" will make surf easy.
http://electronicshelponline.blogspot.com/
Blinking codes details to many popular brand TVs are given. Surf the site with patience.

Check your backlight. It may have burnt out. Easy solution is to get a new tv.

Short in the set prevents power up---not a do it your self repair.

Technika flat 32 screen: Doesn't not switch on, the blue standby light just flashes.

my hatachi hd/1080 tv has a solid blue light on and it wont turn on i push the reset button on the bottom right and it still wont turn on

Check the bulb. This is a common problem.

T.V may have been magnified. Something magnetic too close to television will fry the screen per say. There are repair people with demagnifiers but doesn't always work

lamp door has to be closed