TROUBLESHOOTING PART WITHOUT SCHEMATIC ↓↓↓

These 5 steps have been brought to you by ELEX518. Keep in mind that it doesn't guarantee all parts repair success. BUT definitely guarantees a collection of knowledge making your repair skills stronger over time 😉


1.)The Gathering  
Collect data as much as you can by asking questions. Apply the 5 whys technique. 
Make sure to ask the right questions.

Function of part -Driver? Controller? Power supply?
Failure information -No power? Can't communicate? Errors? 
The last activities before the failure -After reboot? While increasing power? Changing load? 
How did the failure was verified -Replaced with good part? 
                                                       Tested to second machine? Not verified yet?
Technical data -Collect user manual, block diagram, or hard/soft copies related to the part.

      
 There's no harm in asking, better than no asking ")

2.)The Interpretation   

Define and understand each word of information. 

          ex. If failure says "PPMU_OUTHP_DC90LF_C_54P" error
                You must explore, research, and understand what is PPMU? 
                what is OUTHP? what is DC90LF? what is "C" stand for? What is 54P?
Sketch your own block diagram.
          Common Division:
                Power control area Analog/Digital circuitry
                Amplifiers Mux/Demux
                Memory DAC/ADC
Sketch your own schematic diagram, start from the failing area.
          ex-1. When a motherboard got blown diode, you can start sketching schematic from 
                   that diode and expand it until you can see clearly the function of diode. Also from 
                   there you can analyze other components to check that can cause the blown diode.
          ex-2. The power supply contactor trips when turn-on. Thus, start sketching schematic 
                   from that contactor and expand until you may see clearly the other components 
                   that possibly gone wrong and trigger the contactor to trip.

3.)The Checking  
Once you have better understanding with the failure and familiarize the part block diagram then you are ready for components level troubleshooting. Start checking the components related to the failure.

Always check first the power area.
      fuse, diodes, zener, regulators, high power mosfet, capacitors
Perform basic SIGNATURE troubleshooting.
      resistance, capacitance 
      inductance, semi-conductance (diode mode test)
Look for symmetrical circuits.
      Compare signature readings with symmetrical circuits.
Identify and check most electrical stress zones.
      Heat marks
      Edge connectors where the circuit meets.
      The main components.    
      High voltage/current components.

Mark all components involve!

4.)The Action  
Replace components which having out of tolerance signature readings.
Replace components with same date code with the defective (especially relays and capacitors).
Do proactive replace those most possible root cause IC (last option). Because checking IC offline can't guarantee a good one. Record all components that you replaced, you may need it in the future analysis.

5.)The Testing  
Bench test the part after repair to verify fixes (load test or power-up test). 
If bench testing is not possible, try to attend the part testing at customer site to gather further information if failure remain. You may need to continue troubleshooting going back the previous steps. Best of luck! Thanks!

 OPEN  links below for other sites giving tips in Electronics repair.




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