Expert: Cleggsan - 4/3/2009

Question
I have a very expensive system in my explorer. I have a Jl audio w7 12' sub w/ Jl audio 1500 watt amp. I also have four infinity speakers. When i first bought it, it was doing fine but now all of a sudden it will just shut off on its own and ill turn it back on and it will do it again and again. I was told it might be a fuse but im not so sure.

any advice would help

Thanks

Answer
Probably not a fuse; if it were you would not be getting any power to the system.

The shut off action is most often a result of overload to the amplifier.  It can be caused by over driving it (playing the audio too loud for long periods of time causing big heat rise to the amplifier), short on one of the speaker lines, short or loose voice coil in one of the speakers, bad ground on the negative side of the power amp ground line.

Here is what I would suggest:
ONE: Disconnect all but one speaker.  Then try another speaker, etc. trying to find a bad speaker by process of elimination.  
TWO: If you have vom or ohmmeter measure dc resistance of each speaker line by disconnecting at the back of the amp and attache the speaker wires to the ohmmeter.  Resistance should not go less than dc resistance of the voice coil of the speaker at the other end. Most often this is 4 ohms.  
THREE:  Even disconnecting all the speaker wires from the amp and see if it still shuts off.  You can use a known-good, standalone speaker connected to one of the outputs.

By doing the above or some variation of it you can determine if the problem is external,  i.e., a speaker or wiring gone bad OR an amplifier that has internally gone bust.

Hope this helps.
C