Hiss, or white noise 1 - High levels of white noise usually occurs when amplifier level controls are turned up too high - readjust according to the procedures in section ”Setting up systems after installation for best performance” 2 - Another major problem that can cause excessive hiss, is a noisy head unit - unplug the amplifier input RCA cables, and if the hiss level reduces, the source unit is at fault.Įlectrical interference The inside of an automobile is a very hostile electrical environment. Noise problems System noise can be divided into two categories, hiss, and electrical interference. If these are non existent or low, take voltage measurements at fuse holders, distribution blocks, the head unit’s +12 volt and remote leads to localize the problem. 3 - Measure the +12 volt and remote turn on voltages at the amplifier terminals. System does not turn on 1 - Check all fuses. 2 - A short on the main +12 volt cable from the battery to the vehicle chassis will cause the main fuse to blow. 3 - Check all +12 volt and ground connections.įuses blowing 1 - The use of loudspeaker impedances below the recommended minimums will draw more current - check. 2 - Make sure that the battery voltage, as measured at the amplifier’s +12 volt and ground terminals, is 11 volts or more. Low output power 1 - Check that level controls have been set up properly. 2 - Driving high power levels into low impedances - back off on the volume control, and/or make sure you are not loading the amplifier with less than the recommended loudspeaker impedance.

Causes of overheating: 1 - Inadequate cooling - relocate or remount to provide better natural airflow over the fins. If the amplifier seems fine with RCA cables plugged in, connect the speakers, one at a time, and if one of the speakers or its wiring is faulty, it will activate the diagnostic system.Īmplifier heatsink overheating The amplifiers will shut down when the heatsink temperature reaches 80 degrees centigrade, and turn back on once the unit has cooled down below that point. If it goes into diagnostic now, the fault lies in the input, either with bad cables or source unit. If not, plug the RCA cables back, and reset the amplifier. Now turn the amplifier back on, and if the diagnostic LED lights, the amplifier has an internal fault. Should the amplifier go into diagnostic mode, simply disconnect all RCA and speaker leads, while keeping +12 volt, power ground and remote leads connected. 2 - An internal amplifier fault that causes a DC offset on the loudspeaker output. This state of affairs will be indicated by the front panel PROTECT LED lighting up under the following conditions: 1 - A short circuit on the loudspeaker leads.

The key to finding the problem in a misbehaving sound system is to isolate parts of that system in a logical fashion to track down the fault.ĭescription of the Diagnostic system built into all MB Quart amplifiers The diagnostic system will shut down the amplifier, until reset by turning the head unit off, and back on.

Mb quart amp