My sanyo tv will turn on for a second and then turn off.

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electro-medical.blogspot.com/
http://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

You may have a fault in the power supply board and the tv is shutting down in to protection mode

sounds like a defective str power regulator ic .......but my advice get a tech to resolder all the pins at the power suppy board area, there may be some open pins that triggers the on and off episodes

Most likely this is what you need:
http://www.coppelltvrepair.com/p/29/sanyo-dp37819-p37819-01-does-not-power-on-repair-service
Good luck!

take it back

When you turn it on its on for 5 seconds then its turns off by itself

Yes,unplug,replug the tv an hour later.The tv should reset itself back to factory setting and work.Not,than the tv power supply board have problems.That the board,where the power a/c coard plug into it.Tries websites like Shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.

I took Sanyo's advice and bought a new TV

same

SOLVED Turn it on and it turns right off Sanyo dp50747 Plasma TV