How to Repair an Audio Amplifier With a Tutorial

By Simon Foden

Poor wiring, loose components and blown resistors can cause stereo malfunction.
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The complexity of an audio amplifier repair job depends on the location of the damaged part, the type of component that is damaged and the nature of the damage. Audio amplifier repair can range from replacing a fuse in the plug to re-winding the power transformer primary windings. Using an audio amplifier repair tutorial to guide you through the process reduces the risk of mistakes. It's better not to rely entirely on the repair tutorial. Once you've repaired one device successfully, use the tutorial as a reference rather than a guide.

Read the safety instructions. Audio amplifiers typically carry a potentially lethal amount of power. If you don't understand any of the safety instructions, consult a professional. Always unplug an amplifier before removing the back.

Familiarize yourself with the technical terms. You can't use a multimeter unless you understand terms such as "resistance" and "tolerance".

Troubleshoot the amplifier. The "troubleshooting" section of the repair tutorial on the Basic Car Audio Electronics website encourages you to learn the meaning of the various warning lights. If your amplifier is in protect mode, refer to the owner's manual to find out the meaning of the warning light combination.

Turn off the amplifier. Unplug the amplifier and let it cool down for 10 minutes.

Study the layout of the amplifier circuit. Use the wiring schematic as a reference, and use color marker pens to color code the parts as they appear on the schematic with the physical components inside the amplifier.

Unscrew the chassis enclosure, unplug the cable plugs and unscrew the board to expose the circuit board.

Test the circuit. Plug the multimeter probe into the first resistor in the circuit, which is the one closest to the power supply. The resistance reading in amps should be equal to the amount of current in volts, divided by the value of the resistor. For example, a 10-Ohm resistor in a 12-volt circuit gives a reading of 1.2 amps. The tutorial concerning resistors on the Basic Car Audio Electronics website explains Ohms law.

Remove faulty parts. If the resistor gives a reading that is higher than five percent variance, it is faulty. A resistor that gives a zero reading is blown. Replace the resistor by disconnecting the connector pins on the base of the circuit board. Slot a new resistor of identical value into the vacant hole on the board, and solder the connector pins to the connector strip.

Fix loose wiring. If you spot a loose or poorly connected wire, refer to the schematic to establish which component is connected to the wire. Refer to your tutorial to establish what that component does. This gives you an idea of the symptoms of faults for each component. Melt the wire connection with a soldering iron. Wait for the connection to cool, dip the iron in some clean solder and create a new connection.