最好有线路图。如果没有，只好换整个板子。或有耐心，youtube has lots of video:

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.