Help! Lectronic Guru's!

TFOB said:

bought a Brand new "DUEL" Am/FM/CD player for the 78 King Cobra. New speakers also. I have gone through 3 radios since Saturday!!! From Best Buy. Radio works Great Until! When it is playing and you turn the ignition off, give the radio power and it looks like it works gets a signal but no sound. The speaker wires have all been checked and are good. No bad ground wires. Now you take a new unit plug it in and it works, plug the old unit in, and it don't work. Plug the new unit in and go through the turning on and off with the ignition and it quits working.l
Now if you turn the radio off before you turn the car off it is fine. I have a direct wire from the radio fuse with an inline fuse feeding the radio, and grounded to the steering column brace. SO there is a good ground. It was grounded to the lighter so I changed it. I am at a a loss and so is the guy at Best Buy. could the antenna do something??????? I am grasping here. Like I said 3 radios.
HELP

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i love electrical problems in cars. if i had the chance to do all over, i would do that for a living. anyway, this is what i would do. run a DIRECT line to the battery with an inline fuse. must have a fuse....a brand new radio shack inline fuse. run the ground wire to something on the block or the battery itself. don't mess around with interior guess work. buy two NEW rolls of wire from radio shack..red and black..or the roll with the both together and run outside the car with the doors open and hook directly as i mentioned. this way, there is no doubt about anything! then, if all works as it should...concerning power, reconnect the ground first where you originally had it. and retry. and so on. you may just have to turn on and off the radio when you leave the car and forget the ignition connection. i've seen garbage in steering columns that cause major problems and/or bad fuse boxes. to futher test the SOUND...be absolutely sure you have direct new wires to the amp, both pos and neg...no old wires and NO connectors in-between. regardless how much you test, connectors to the speakers are a pain in the a** and work when they want. condensation kills sound. many times if there is ONE bad connection to one speaker, it breaks down the entire output chip of the amp. be sure to check the OHMs of the speakers you are using and compare to the output of the radio....that will kill an amp chip as sure as anything. write me back for updates.

Did you run new speakers wires or are you using the factory connections? Which Dual unit did you get I've been checkin them out at Best Buy also like $179 for the one I want (XD7500 model).