Sp Gupta , Hi , I applied the 13 volts to the test port on the sanyo dp42740 , but still the same thing .

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://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.
Before going further; try a hard reset first. If it does not help you, replace the main digital board. There are two methods to reset TVs. The first is simple to do; a Hard Reset. The other is somewhat skilled; is a Factory Reset (System Reset). To make it a hard reset, just unplug the TV from AC mains wall socket, and re-plug it back after 15 minutes or so. If you do this by overnight is better. This procedure will make it a hard reset. If you want to make it a system reset [Factory Reset]; you have to enter its service mode option, and select the factory reset option. If you wish to get some details; visit the site linked here.

Hi Gray,
Please try giving 13V from external source. When we exhaust all the options of changing boards we try such things to get the set working. I hope it helps.
Good luck

Yes. If it has shorted component/s. If you wish to get some details; check the site linked here. Pull up older posts. Surf the site with patience. http://electronicshelponline.blogspot.com/

Order your boards from the manufacturer of the TV go to their website they be happy to send them and I will get a refund from shopjimmy

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.

There are several fuses on the power supply board.

The main one is right next to where the cable from the AC connector is on the power supply.

BTW you may want to check these listings too:

http://www.coppelltvrepair.com/search?q=DP42740

(although if you are looking for a fuse that probably means totally dead TV and if that;s the case then you do not need a main board repair)

You cant find bad caps by just looking

USB port is located on the back of unit next to the Antenna input. See page 6 of: http://us.sanyo.com/dynamic/product/Downloads/DP42740%20(355--)-25942323.pdf