IOC Light

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#1 seanjones

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Posted 12 March 2005 - 05:36 PM

I am having frequent issues with the com-tech 400,800 & 1600 and their IOC function.   It seems that intermitently the IOC light will pop on, on one of the channels, disabling signal to pass through that channel.  This occurs with speaker wire and XLR plugged into the back of the unit.  Now I also have on that has nothing plugged in at all and there is an IOC light on.  Anyone hear of this problem before?  Thanks

#2 DGlass



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Posted 14 March 2005 - 02:31 PM

Are these amps being used with a 70 volt speaker system?
If so are you pushing full range music through the speakers?

The reason I ask is that 70 volt speaker systems use transformers at the speakers and these transformers are usually not designed to handle low frequencies. If you do not have a high pass filter on the input signal, to block the low frequeciencies from being amplified, the transformers will saturate at the low frequencies and act as a short to the amplifier. The amplifier will then go into current limiting shutting down that channel of the amplifier and lighting the IOC indicator.

If you have an amplifier with nothing plug in or hooked up and you are seeing IOC lights on than the amplifier needs to come in for service.

The IOC circuit Compares the Input signal and the Output signal and looks for any difference (other than amplitude) of .05%. If IOC is lit and there is no input signal than the amplifier has something broke down inside. This could be an output device, a pre-driver or a multiple of other things that may be causing this. Without it being benched it would be impossible to say what exactly is the issue.