How to Read the Circuit Board on a Car Audio Amplifier

If you like high quality audio playback in your car, you may have a dedicated amplifier to power your car stereo. The complexity of repairing car audio amplifiers depends on the nature and location of the problem. Understanding the layout of the circuit board is key to quickly locating a fault with your car audio amplifier. In order to test resistors, capacitors and transformers, you need to know how to read the circuit board. Using the amplifier's wiring schematic as a reference makes this task a lot easier.

Acquire an accurate wiring schematic. The wiring schematic denotes exactly how the car amplifier circuit is laid out. It contains all of the information you need to understand the physical circuit. These are available from the amplifier manufacturer. The Valve Audio website also has some car audio schematics for reference.

Learn the symbols. To save space, wiring schematics feature symbols that tell us important information. Resistor values are indicated with an ohms signal on the schematic. A large black circle over two lines denotes two wires that are connected. The Learn C website has a list of key references explaining the meaning of the various symbols.

Dismantle your car audio amplifier to expose the circuit board. Turn your car ignition completely off. Unscrew the top of the amplifier to expose the circuit board.

Find the start of the circuit. Trace the wires back to the power supply section. The power supply section is typically a square metal block on the edge of the amplifier chassis. Use the schematic as a reference, and trace the circuit from start to finish.

Make a list of the components that you can visually identify, and use a highlighter pen to mark them on the schematic. Colour code the marks on the schematic by leaving a small mark with the same pen on the actual component.

Identify the ground path. In almost all circuits, the ground wire is black. Trace this wire from source to end. All components connected to the ground wire are also grounded. The International Electrotechnical Commission governs the standard by which circuits and wires are colour-coded. Refer to their website for more information.

Make a note of the surface-mounted component values. Resistors and transistors are mounted flat on the board. They have their value written on the side. The value of a resistor is essentially a measure of how much it governs the flow of the current. It is written in ohms.

Learn the relationship between the components. Items that are connected will be marked as so on the schematic by a straight line running between them. It is essential that you know which items are connected and which are not.


Use a magnifying glass to read the symbols on the side of smaller components.


Never attempt to remove or work on your amplifier while the car ignition is on.

Things You'll Need

  • Schematic
  • Screwdriver
  • Highlighter pen
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About the Author

Simon Foden has been a freelance writer and editor since 1999. He began his writing career after graduating with a Bachelors of Arts degree in music from Salford University. He has contributed to and written for various magazines including "K9 Magazine" and "Pet Friendly Magazine." He has also written for