kevrains

Hi, this is code elated but I'm not after a code. My car was fitted with a faulty alternator and when a replacement was fitted the radio no longer accepted numbers. All the lights come on asking for the code but its impossible to input a code as no numbers appear when pressing the buttons. I've tried holding various buttons down etc, but no matter when it comes to inputting the numbers nothing is coming up. RAC guy couldn't get it to work when he fitted a battery and my mechanic can't see any problem ie its not fused. Has anybody got any ideas what my next steps should be? Thanks for any help.
Cheers