The other day I bought a TV from a yard sale and I needed a code for the remote control. The problem is that it did not come with a manual. So I did some searching and I found a fantastic site that has tons and tons of manuals. Essentially you just find the type of product you need to know about. Once there you choose the maker and the product code. It should display all the information. This site really allows you to feel comfortable about buying electronics at places like yard sales without having to worry about missing information. Give it a try.
Note: I use a lot of quotes but this one is special. He is one of my favorite authors.