Quote Originally Posted by Century7667 View Post
If we could just locate a schematic......
The Delco factory service manuals contain full schematics of these radios. You can sometimes find used copies on ebay. Just be sure that it covers your radio's model number.

Another option might be the Sam's Photofact AR (auto radio) series manuals. A while back I picked up an original AM/FM radio for my 74 Nova ... got it cheap because it wasn't working. I didn't have any luck finding a Delco manual for it but I did find a Sam's that was just as helpful. I probably would have found the problem (a shorted filter cap in the power supply / voltage regulator section) without the schematic, but having it available made it quick & easy. I'm not sure what kind of coverage the Sam's AR manuals have for the 80's & 90's Delco radios though.