Just like with cars, all the same models typically have the same problems. We look up the model # on our repair database to see if there is a common problem for your TV model that matches the symptoms you are experiencing. There are some problems that we just have no idea what the problem could be without checking it first. About 7 out of 10 problems we see in the shop are common problems.
The estimates are not 100% accurate. But most often we can get a pretty good idea of what the problem could be and give you an idea of the price it might cost. We would still have to check the set to be sure.