Ford Radio

[Littlejohn]

A bit of a change from the usual request for radio codes!
I recently bought a N reg, smiley front Transit and I cannot get the radio to respond to any input. My guess is that a previous owner, not knowing the correct radio code kept on trying various combinations until the radio got fed up with him and locked its self up?! If I'm right is there any way to re-activate it. (there is power to the unit, but it will not accept any code input.)