Instantly blows the 5 amp fuse next to the power cord plug.

You probably had a voltage surge. Most sets have a component called a varistor on the power supply board. If you pop off the back you should see this varistor near the fuse. I should look blown or brown or defective in some way. Varistors sense voltage spikes and fuse the positive and negative of the supply together to send the voltage spike back through the ground and save the rest of the electronics in the television, but this results in blowing the fuse instantly when you plug the set in. The varistor will most likely have a disc shape to it, and possibly a brown-orange color. Most of the time you can just cut out these components completely with a pair of wire cutters and the problem will be solved after you replace the fuse. Just make sure to plug the set in to a surge protector because the sensitive electronice inside the tv will no longer be protected from voltage spikes! Hope this helps!

You have a short in the power supply. Look at the regulator and or rectifier diodes. These are all on th primary side of the SMPS (switched mode power supply) the secondary side if shorted shouldn't cause a blown fuse at all.