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Canon LBP 2900B Laser Printer Power Supply Board Problem

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    #1

    Canon LBP 2900B Laser Printer Power Supply Board Problem

    Hi everybody, I am new to this forum.

    Please help me any one of you for my problem.

    I am a computer service engineer. I got a Canon LBP 2900B laser printer from my customer for service. It doesn't on. When i deassemble the printer, i could see the power supply circuit board ( RM1-2316 / 200V ) a resister (0.22 ohms) blown in the primary section. The blown resister is between 39mfd/400v capacitor and a switching transformer, this transformer is between the primary section and secondary section. A K2700 transistor is connected between the above said capacitor and transformer and also a YG862C15 transistor is connected to this transformer in the secondary side.

    I checked all the components nearby blown resistor are good, then i replace the resistor, again it blown, i confused and i decided to change the above said two transistors, again the same resistor blown, what would cause the resistor to blow.

    The sticker on switching transformer is (28EC-237 / TDK X 0933) 5 pins in the primary and 3 pins in the secondary which seems to be good, but i am not sure. how to solve this problem. plz help me. Thank you.
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    #2
    Re: Canon LBP 2900B Laser Printer Power Supply Board Problem

    Clear focused pictures following my directions below exactly helps us help you.
    --- begin sig file ---

    If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

    Please do not post inline and offsite as they slow down the loading of pages.

    --- end sig file ---

    Comment

      #3
      Re: Canon LBP 2900B Laser Printer Power Supply Board Problem

      Originally posted by RKRAJU View Post
      It doesn't on.
      I think you accidentaly a word there.

      Anyway, where do the traces from the resistor go?

      Comment

        #4
        Re: Canon LBP 2900B Laser Printer Power Supply Board Problem

        Most likely when the primary side transistor blew, the drive circuit for it popped too, causing the new transistor to be turned on all the time.

        Check the rectifier before the 400v filtering cap, make sure it isn't shorted.
        Remove the switching transistor and measure the resistance between its gate and the positive of the filter cap, and do the same with the gate to negative of the filter cap. Please report to us the resistances.

        The K2700 transistor is a 2SK2700 N-Channel MOSFET. The pins are from left to right: Gate, Drain, Source. (Looking at the front of the transistor that is!)
        Muh-soggy-knee

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          #5
          Re: Canon LBP 2900B Laser Printer Power Supply Board Problem

          Welcome, RKRAJU !
          The YG862C15 "transistor" is actually a high voltage 150V 10A twin common cathode schottky rectifier.
          My first choice in quality Japanese electrolytics is Nippon Chemi-Con, which has been in business since 1931... the quality of electronics is dependent on the quality of the electrolytics.

          Comment

            #6
            Re: Canon LBP 2900B Laser Printer Power Supply Board Problem

            Hello...
            is ur problem solved or not ,I don't know.But the problem is with one smd transistor backside of this board,which is feedback triggering pulses control of main MOSFET K2700.checkup that transistor.

            Comment

              #7
              Re: Canon LBP 2900B Laser Printer Power Supply Board Problem

              Hello friends, the topic is a bit old, but I have the same problem, I would appreciate if you could help me find a solution. Likewise, a 22 ohm resistor explodes. I change, it explodes again. Where exactly you call this MOSFET K2700, pictures are attached.
              1-
              2 -
              3-

              Thanks all

              Comment

                #8
                Re: Canon LBP 2900B Laser Printer Power Supply Board Problem

                Originally posted by haylaz_prens View Post
                Hello friends, the topic is a bit old, but I have the same problem, I would appreciate if you could help me find a solution. Likewise, a 22 ohm resistor explodes. I change, it explodes again. Where exactly you call this MOSFET K2700, pictures are attached.
                1-
                2 -
                3-

                Thanks all
                1 - https://prnt.sc/239gv5u
                2 - https://prnt.sc/239gy4e

                Comment

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