3 blinks is short protection on this model---98% chance one of the two STK-392-110 Convergence chips it uses has shorted.
If you unplug set and look inside you will find two black chips that have that number printed on the front of them in white letters. Right in front of them you will find about a dozen light blue resistors---most are marked 2.2 ohms---look if you get a chance---if even one of those resistors is white in the middle (discolored) you have found your problem.
Both chips and any bad resistors need to be replaced.
The repair involves getting at the parts and replacing them--the chips each are mounted side by side on metal heat sinks with fins--each has 18 pins.
Most shops get 300 or more for this repair but the actual parts cost if you or someone you know can do it is under 30 dollars.
I have START TO FINISH, STEP BY STEP INSTRUCTIONS FOR THIS REPAIR IN THIS SET. I got a notice from a lady who used them to fix the same set you have---she saved the set and a lot of money.
The instructions tell you everything you will need and how to do the repair----clearly I do not know how much skill you have---it involves soldering etc.
If you want the instructions I will post them here for you to look at and copy/ paste them. Once you read them you should know if you can do the repair------they are my own instructions based on doing this repair hundreds of times.
I will also post a photo here showing what the chips look like.
Repair takes me about 1 hour; if you are doing it for the first time it will take you longer.
I also know the best place to get the chips at reasonable price.
If this information has helped you rate this solution as I do this here for free.
SD TECH