Problem with Wi Fi

I have a desktop computer with Windows 7. I have been doing computing for a good many years but do not consider myself to be a guru by any means. I finally got a Smart TV and decided to install WiFi so that I could access the Internet with TV. For a few days everything seemed to be working but then I began having a problem accessing the Internet with TV and also computer. I had installed a Linksys N300 Router, Model #E 1200-NP.
Signal Strength at the TV was 3 of 4 marks. I could use a little advice here. Does this appear to be a defective modem? If so, should I just replace it with another of the same model or should I get a different manufacturer's product? Any recommendations?

Bob P