No manufacturer in business. No support. Any repair would cost more that the brand new value of the device. You might try to find it on eBay but ai saw only one there and it had finizio written across its image. You will not find a service manual. Below is what someone with some skills did but you should really look for another product.
http://digiassn.blogspot.com/2009/01/tech-fixed-tv-for-father-in-law-dtd1363.html
Need more details. Is it an hdmi hookup or a coaxial? Is your cable line hooked up directly to the TV or are you using a modem? Is it a smart TV or just regular?