Comparing Identical Circuits For Troubleshooting
If you are repairing equipment that have two (like LCD Monitors) or more similar circuit (like TV R,G,B) then you can compare the circuit and find the solution fast. Many times when troubleshooting the LCD Monitors (especially the one that is new in the market or the model that you have not repair before) that have problem in the inverter board (display shutdown after few seconds), i always compare the top and the bottom circuit. I will use analogue ohmmeter to compare both the circuit. By right similar circuit will have similar ohm readings and if there is any differences in the resistance reading then you know that something have gone wrong. It will be the clue for you to troubleshoot on that particular area. You can compare the transistors, high voltage transformer or any components in the circuit. In certain circuits you may have to discharge the cap voltage as it could affect the meter’s reading.
If you have the scope you can also use it to compare the signals between the circuit. For example, comparing the waveform of the Red and the Blue circuit in TV/Monitors. It should have slightly similar waveform and if you got any out of shape waveform then you know there is a problem in that circuit. If you have the Huntron tracker that will be even easier because Huntron was designed to serve this kind of purpose.
The best way to improve your skill in comparing the circuit is to understand how the circuit works first with the help of some schematic diagrams. Try get a good equipment and start to compare the circuits. Write down all the important info you have measured for future reference. With this way you will ever ready to compare any circuits that comes in to your repair bench.