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Confusing Circuit Board Marking

By on August 27, 2012

diode marking

Sometimes I do not know why manufacturers have to make our lives so difficult by labelling components marking not according to standard code. If you take a look at the photo you could see the marking for capacitor is "C", resistor is "R" but the diodes they labelled it as "CR4" and "CR5". They can just print it as "D4" and "D5" and that's it. You can know the components are diode because there are a band in the body. What if this is a 3 legged component with weird part number and the board marking is assuming "BP"?

It could be a bipolar transistor, fet, triac, SCR and some other components. We as seasoned repairer sometimes could figure it out what type of category the component would be but what if a beginner try to repair such board? The beginners will get confused and give up on the repair work.

Not only board marking, there are currently many components in the market that have funny and weird part numbers. Doing a Google search on those part number yielded zero result! Sometimes the semiconductor manufacturers will cut short the part number and you have to guess what will be the complete part number. It can be frustrating especially you found the bad component in few minutes but take hours to find the part details or datasheet or the subsitution.



  1. jojogreg

    August 28, 2012 at 11:59 pm

     i agree to you mr.yong,that's really make our lives difficult in recognizing that kind of labelling.I wonder why they make that kind of labelling,that's an additional headache in troubleshooting..

    • Jestine Yong

      August 29, 2012 at 12:27 am

      Hi Jojo,

      Sometimes even the experienced repairer also have a hard time to figure it out.


  2. RD Electronics

    August 30, 2012 at 2:02 pm

    I found some times marking letter is OK, but marking polarity on the board is wrong. So, I always look for the  (-) on the electrolytic caps and I check the mark on the board, I don't want to make a mistake when I put the new one. 

  3. jumbe mateyu

    September 6, 2012 at 12:10 am

    This is very true Jestine and it is common these days.I came across  a faulty amplifier in which main transistors were marked BCE or Base,Collector and Emitter yet  their part number showed that they were not  bipolar transistors as indicated on the board but FET transistors,GDS and once I replaced them, the amplifier worked perfect .

    • Jestine Yong

      September 6, 2012 at 3:45 am

      Hi Jumbe,

      I have seen this problem also in CRT Monitor many years ago.



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