Audio Systems: dead sound, output transistors, speaker wiring

Question
i just purchased a aftermarket used head unit (jvc). I hooked it up and after orking great for 3 days the sound went out. the radio powers up fine and evcerything works great just no sound. is it possible that the amp in the radio went bad? any help would be greatly appreciated. thanks chris

Answer
Chris,
Yes.  Since you didn't give me the model number and the automobile I cannot give you specific advice, but here are some general comments that may help you.

ONE:  If the unit is powering on properly but not sound from the amp, check to see if the wiring harness connector has come undone.

TWO:  Check to see if the clips on the back of speakers have fallen off (unlikely that both or all 4 of them fell off at the same time, however).

THREE:  In order to check positively that the amp is or is not working the best way is to get a small, loose speaker and a few feet of zip wire; then connect that speaker to each amplifier one by one.  To connect to the unit you may have to get into the connector or if there are pigtail wires coming out the back, slice off a short 1/2 inch of insulation so you can wrap the speaker test wires right onto the output wires.  Then, of course, after the testing, tape over the exposed wires so they will not short out.

If you find the amp IS working, then you you have either a power ON problem or a speaker wiring problem.....

If the amp units are dead the output transistors have probabely failed.  This would happen if the wiring was wrong or if there were shorted loads over one or more of the speaker lines.  If the amp outputs are dead they are quite expensive to repair - parts and lots of labor.

Hope this helps.
Cleggsan