https://www.youtube.com/results?search_query=hotw+to+spot+which+broken+component+on+a+circuit+board
For example,
This one has a circuit diagram:
https://www.youtube.com/watch?v=ye9dguKy_Cs
so the owner of the video
1. checked the power supply at 3:40
2. checked the path of the signal at 4:00
3. checked signal out put at 5:20 ( one could use an oscilloscope to see the waveform)
4. at 11:50, and 12:20 the faulty spot was found
5. fixed the problem at 12:25,
6. the correct signal is at 13:23.
Another example:
https://www.youtube.com/watch?v=i293n9VVpHg
The third example (long and boring):
How to Troubleshoot Electronics Down to the Component Level Without Schematics 49:23
1. visual inspection at 1:50
2. use a multimeter at 5:38,measured the bridgerectifier at 18:00 and individual components at 20:17
3. power up,at 21:05,
This video is so long and so boring, I stopped here.