Radio issue 93 GMC 5.7 L 4X4, 210000miles

Having problems with radio in my 93 gmc suburban. It has a am/fm stereo with cassette and graphic equalizer which is all factory equipment. With key in accessory position, or on position before and after the start of truck the radio will light up and has power, but I am unable to change stations move the volume control up or down. There is also no sound produced by the radio. The radio has the ability to be turned on and off and clock comes on after station is displayed but it does not advance. Could this be and issue with a relay? Or do you think it could be that the radio is wearing out and needs replaced? I have checked all fuses and they are in working order. I have also changed the ignition switch thinking that the contacts within the switch may have gone bad but it still does the same thing after replacement. Any help would be great! Getting tired of the silence.