As television repairmen many of us have found it necessary to replace whole circuit boards on occasion rather than replacing individual components due to the time involved in troubleshooting on a component level, and we often buy salvaged circuit boards from TVs that are advertized to have been damaged in shipping, Over time many of us came to discover some sellers are lying about the origin of their circuit boards, and they don't really know if their boards are working, so they let you figure that out.
I often use ebay to purchase salvaged circuit boards, and I've had some degree of success, but I've also discovered it can be one of the worst places to purchase them due to dishonest sellers, Ebay has a buyer protection policy, and most sellers will refund your money if there boards don't work, but having to return a package and reorder another board is a waste of our valuable time.
I don't have a remedy to assure every board you buy is going to work, here are some things I've learned to consider before purchasing a second hand boards on ebay..
Look at the sellers feedback ((in detail)) and read the negative comments. Even though the seller may have a high feedback score, It may come from selling items unrelated to salvaged circuit boards. Also note that many buyers who have had problems with sellers have agreed to cancel the transaction and never left any feedback, so you can't tell how many orders have been cancelled by looking at their sellers feedback.
Another thing to consider is the sellers return policy.. Many sellers expect you to pay the return shipping cost even when they sell you a bad board. That alone would make me suspicious.
If you do purchase a defective Circuit board on ebay, and the seller wants you to resolve the matter through his direct email address don't do it. Ebay has a contact seller link which archives a verifiable record of your email transactions. This may be important if you need to contact ebay to make a complaint about a bad seller who don't settle with you fairly.
If you do have an issue with a seller I was warned not to make any threats or use abusive language when trying to resolve your transaction issues. This can be used against you by the seller if ebay gets involved.
In the last couple months I purchased Three circuit boards on ebay and Two of them were no good. When I asked the seller if they expected me to pay the return shipping for their defective boards both sellers told me to keep their boards. The up side of this is I may be able to repair their boards easier than my own, but at the very least I got some free spare parts at the sellers expense because of their dishonesty. I think it's called poetic justice :-)
DBA Dave's TV in Grants Pass Oregon. http://www.tvrepairinfo.com/