Fixing Car Audio Display

[tmho]

The display of my car audio (radio and play CD & MP3) recently became very dim that I can hardly see. I mean the "letters or characters" of the radio channels and the name of the songs but not the light for the buttons. Can somebody please give me some advice on how to fix the problem? Thank you. (I bought it about 2 years ago. The brand name is Dynex and is not a famous one.)