A typical Printed Circuit Board (PCB) contains a large number of passive and active electronic components connected together with traces on the board. These traces are generally made of thin strips of copper. To troubleshoot a PCB, you may need to follow the path of current flowing through these traces. This can be done with the help of an oscilloscope.
Instructions
1 Identify the point on the board from where you wish to follow the current. This point could be a pin on an electronic chip or the terminal of a passive component, such as a resistor or capacitor. If you are trying to diagnose a problem on the board, it is better to first identify the current path on the circuit diagram, if one is available. If the circuit diagram is not available, you will have to investigate each component by following all of the current paths of its inputs and outputs.
2 Turn on the oscilloscope and insert the probe into a socket on Channel 1. Gently pull out the plastic cap on the tip of the probe and place it in a safe place where you can find it later. You will see a bare pin sticking out of the probe's tip. This will be used to trace the current path.
3 Identify a good ground point on the board and connect the ground clip of the probe to that point.
4 Provide the PCB with power and turn it on.
5 Touch the current path's starting point with the tip of the probe and press the autoset button on the oscilloscope. Do not remove the tip from the starting point until the scope has set all of the parameters according to the signal it is seeing at the starting point.
6 Visually follow the trace, moving forward from the starting point. Touch the probe to the first terminal component that you encounter. If you are still seeing pulses in the oscilloscope, it means that the current is flowing. If you do not see anything, it means that the copper trace is broken. In this case, touch the trace halfway between this point and the starting point with the tip of the probe to see if signal is there. If there if signal, move forward. If there is no signal, move backward. Ultimately, you will be able to find the point where the trace is broken. If, on the other hand, you were able to see the signal at the component's first terminal, test its other end. If you do not see any signal, the component may have gone bad and will need replacement. If you see the signal, move forward by following the copper trace.
