93 cougar xr7 radio problem

pretty much stumped on this one. Hopeing someone can shed some light.

I put in a aftermarket Head unit and it worked perfectly untill I turned the volume up about 3/4 of the way... It shut off and wouldnt come back on. check fuses etc all good, Put the stock am/fm/cassete payer back in and now none of the buttons are functional except voume knob and cassete player...... The stereo is just static with random stations coming in/out. none of the buttons work...

It seems like somewhere between the radio fuse and stereo something got messed up ? I checked what i could see and it all looked fine.

also I hooked the aftermarket head unit up in my truck after it randomly shut off in the cougar and it works fine still.

Right now im stuck with a $200 cd player that i cant even hook up yet, and a stock am/fm cassette deck where only the cassete part works....

PLEASE HELP :(

took it to a local stereo place and they wanted over $50 just to look at it...

anyone ?

Some of the Cougars have an amp mounted under the center console area. I wonder if maybe somehow that didnt get fried? Or perhaps a ground wire got pulled and isnt making a good ground. Or even a 12v supply wire. Sounds like a real odd problem. I had no issues with my '96 when installing my unit, other than trying to get all the wiring stuffed into the small slot.