How to Troubleshoot a PCB

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Typical Printed Circuit Boards, or PCBs, contain a large number of electronic components connected together through thin copper traces. The density of components and traces on a PCB depends on many factors, such as size constraints, the amount and type of electronic processing required and the type of components used. Some boards are also multi-layered in which some traces run through inside of the board as well. Troubleshooting a highly dense and multi-layered PCB is extremely difficult and requires specialized equipment. However, one can troubleshoot a two-layered board with some simple instruments.

Things You'll Need

  • Magnifying glass
  • Multimeter
  • Inspect the PCB using a magnifying glass under bright lighting conditions for any shorts, disconnected component pins and broken signal traces. Start from a corner and slowly perform a visual scan of the board. Mark the problem spots on the board with fine marker.

  • Identify the power input to the board. This is the input that is connected to the power supply, which could be an AC adapter or a battery pack. The power input will be connected to a voltage regulator on the PCB. Identify the input pin of the regulator. This is the pin that will be directly connected to the power input to the board.

  • Turn the multimeter on and set it to DC voltage measurement mode in 20-volt range. This is generally done by turning its knob to the point marked with two parallel lines and "20V". Insert the red lead of the multimeter in the socket labeled "V" and the black one in the socket labeled "COM".

  • Supply power to the board by connecting it to either its battery pack or its AC adapter, as the case may be. Gently press the ground input pin with the tip of the black multimeter lead. The power input has two pins, one is connected to the voltage regulator input and the other to the ground plane of the PCB. The one connected to the ground plane of the board is the ground pin. While keeping the black lead tip on the ground pin, touch the red lead tip to the power input pin. The multimeter should show the input voltage value corresponding to the rating of the battery pack or the AC adapter. If the correct voltage is not displayed, the battery pack or the AC adapter is malfunctioning and should be replaced.

  • Gently press the ground input pin with the tip of the black multimeter lead and keep it there during this step. Touch the tip of the red multimeter lead to all the pins of the voltage regulator one by one, except for the voltage input pin, while keeping an eye on the multimeter display. At least one of the connections should show the output voltage of the regulator, which generally has a value of five volts in most PCBs. If none of the pins shows any output voltage, the regulator has gone bad and should be replaced.

Tips & Warnings

  • Do not use a lead pencil to mark problem spots on the board since the lead may cause electrical shorts between the traces.

References

  • Photo Credit Jupiterimages/Photos.com/Getty Images
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