According to the service manual that 4 blinks count does indeed point to a defective power board part #ETX2MM806ASH .
You can buy that board at the link below for $116 ;
By the way , never mind the model number there , this boards fits in various models
I don`t know if you had in mind to look into repairing this yourself but If that is not your cup of tea so to speak then to have this repaired at home could cost you around $250 to $300 parts included and perhaps $50 less if you take it to the shop yourself .
If you need to find repair shops near you then look at the link below and enter your zip code ;
This will give you a list of NESDA member repair shops in your area.
This list may be limited though and you may find more by simply using the yellow pages or simply google "tv repairs" and the name of your town .
You could give a call to different shops in your area to get an idea of their rates , it pays to shop around .
but if i may be frank , considering the age of the tv at 6 or 7 years old and the fact that you can get a new 50" tv with all the bells and whistles for around or less than $500 ,I would think twice before investing that kind of money into this one.
I think your money would be better invested in a new tv .
Let me know if you have other questions and if not then please do not forget to rate by clicking on the star icons at the top, then click on Submit so i get paid for my time helping you .
Also note that it will not close this post , you can come back here at any time if you need further info or help .