Display lights go out after 30 seconds

It could be a short in the radio's wiring, if you know what you're doing it should be easy. Open the radio's case and locate the wires that are connected to the radio's LED display lights and check for any kind of error such as a split end or burn mark. Most commonly it is because of a manufacturer error. If you don't fee comfortable working with it yourself, take it to a radio repair shop and have them look at it. But seriously, in my opinion, never buy anything on eBay, you never know what you're getting yourself into.

Best Regards,
Gavin93