I just bought a faulty DX6 off eBay £60, I thought it would be good value for spares.
First thing I did was take it apart but nothing visual. Next I googled for Spektrum system faults and found a very nice post on resetting
Result fixed!!
It was the first firmware version 1 and I've successfully updated it to the latest just out this month version 1:20
Screen protection has never been removed so it is like brand new