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.
We need as much information as possible. The minimum information we need is Make (Sony, RCA, etc.), Model and/or Chassis (should be on the back cover), TV type (CRT, CRT big screen, DLP, LCD, LCD projection, Plasma) and the problem it is having.
Other information that can help is Manufacture Date (back cover).
Most sets can be repaired the same day or next day. It may take longer if we have to diagnose an uncommon problem (like problems caused by pests or power surges). Also, if parts are not found in San Antonio, ground shipping from the most common distributors can take 4-5 days.
This is the fee we charge to diagnose electronics components. With few exceptions, the most difficult part of TV repair is figuring out what the problem is. We charge a fee for putting the set on our "bench" and troubleshooting it to find out where the issue is and what needs to be done for repair.