Aiwa CT-X409 Car Cassette Player

I had an Aiwa tape deck, model CT-X409 and I bought it while it was on sale. The first thing I did wrong was buy it from Best Buy. They have good products and cheap but if you don;t buy the stupid $20 warranty, you're screwed. I hooked up the radio and I had it working beautifully and it was a great radio for the price I paid; $100. Then one day while I was driving, it cut out on me. I hit another bump and it came back. The radio was still on but I heard the sound went dead with a "whump". I took out all my connections and redid them but the same problem occurred. I called around to find out what the hell was the problem and people told me that I fried it because I brought all of the speaker grounds back to the radio. I normally ground the speakers by themselves to the chassy of the car in all of the other cars I'd done before but I never had an Aiwa before so I thought that I'd follow the directions step by step and hooked it up right as the professionals would. I went to bring it back to Best Buy and tell them that it was fried and they said that if I didn't buy the stupid $20 warranty, I was screwed because even the factory guarantee couldn't do anything without the $20 warranty. It was a good radio while it worked but it screwed me over. If you hook it up without the speakers ground to the radio, it might be okay but then again, it might not. It's your choice it you want good sound for a cheap price. Take the chance.