@DeeJay Tev > Did you sell it to someone in a country whose voltage is different than yours? It could be the circuitry was damaged even though the fuse was blown.
The other thing to check is that the serial number of the unit you received back is the same as the one you sold; I heard of a case where a user bought a CDJ from a guy on Craigslist, then told the seller the unit wasn't working, swapped his dead unit with the one he bought and gave the dead one back to the seller.