1981 Corvette Delco radio

Hello: A Delco radio from a 1981 Corvette came across my work bench. It must be the top of the line for it's time; it is electronic tuned, and auto reverse cassette. Unfortunately, all the stickers for model and serial numbers have fallen off the radio's case. The complaint is hiss, but no tuning, no display, no music. I applied 12Vdc, and the complaint is correct. The display is dark, and only a small hiss in the speakers. I actually repaired Delco car radios back in the late 1970s when I worked for a local service shop while in high school. I have forgotten much about these, but remember that for the most part, Delco radios were reliable, and generally simple to fix. With this radio, I am not sure where to start. A schematic wouyld be helpful, but I do not havethe model, and do not know where to get schematics. Any advice, and assisatnce is appreciated. Thanks, Bill