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Please help to fix this PA-1151-03HS-ROHS power adapter

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    #21
    Re: Please help to fix this PA-1151-03HS-ROHS power adapter

    Hmm. What part number is printed on the primary switching IC a that drives the mosfet?

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      #22
      Re: Please help to fix this PA-1151-03HS-ROHS power adapter

      Originally posted by CapLeaker View Post
      Hmm. What part number is printed on the primary switching IC a that drives the mosfet?
      The part number is difficult to see. There are 3 rows. I can only see the last few numbers/characters on each row as follows.
      02N
      S107
      0031
      Attached Files

      Comment


        #23
        Re: Please help to fix this PA-1151-03HS-ROHS power adapter

        I don't think those small caps or the mosfets are the problem anyway. Your issue is strictly on the primary side, it's where the AC voltage comes in, get rectified to DC then stored in the 400V cap.

        Since the 19V DC output is only generated when 290V DC is present, and not when it's 170V DC, seems clear to me that either the bridge rectifier is failing or the 400V cap is.

        Comment


          #24
          Re: Please help to fix this PA-1151-03HS-ROHS power adapter

          The voltage itself of 290v is completely wrong as written on the previous page.
          Please measure your house mains voltage and see if you get a sensible reading.
          Then a 12v battery and see if you get a sensible reading.
          If you do we can assume the meter is ok and the only likely fault condition is the PFC stage.
          Only problem with that is I don't know how fucked up it would need to be to generate such a voltage.
          "The one who says it cannot be done should never interrupt the one who is doing it."

          Comment


            #25
            Re: Please help to fix this PA-1151-03HS-ROHS power adapter

            set the meter to AC and meter the cap - it will show you the ripple/noise

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              #26
              Re: Please help to fix this PA-1151-03HS-ROHS power adapter

              Originally posted by прямо View Post
              I don't think those small caps or the mosfets are the problem anyway. Your issue is strictly on the primary side, it's where the AC voltage comes in, get rectified to DC then stored in the 400V cap.

              Since the 19V DC output is only generated when 290V DC is present, and not when it's 170V DC, seems clear to me that either the bridge rectifier is failing or the 400V cap is.
              Please note, if the power supply is not connected to the computer, then sometimes, I can get 19V DC while the voltage of the 400V cap is fluctuating in between 210V and 170V. Then under such condition, once connected to the computer, the voltage of the 400V cap stays at 290V and the computer will be turned on (if last time the computer was off by itself) for a certain period of time. And then after manually turn off the computer, the voltage of the 400V cap drops and stays at 170V.

              For the 400V cap, in my #10 post, I have mentioned that I added a 220uF 400V cap in parallel with the existing 150uF cap. Will this mean the problem is not from the 400V cap?

              For the bridge rectifier, I have checked it on the board. There is no short and the forward bias is normal. Do I need to remove it from the board to check it?

              Comment


                #27
                Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                Originally posted by Per Hansson View Post
                The voltage itself of 290v is completely wrong as written on the previous page.
                Please measure your house mains voltage and see if you get a sensible reading.
                Then a 12v battery and see if you get a sensible reading.
                If you do we can assume the meter is ok and the only likely fault condition is the PFC stage.
                Only problem with that is I don't know how fucked up it would need to be to generate such a voltage.
                Yes, I have checked my house mains voltage and my car battery and confirm that my meter is working properly. I have also used an analogue meter to confirm the voltage of the 400V cap are 170V and 290V under different situations.

                Sorry, I do not under what PFC stage is.

                Comment


                  #28
                  Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                  Originally posted by stj View Post
                  set the meter to AC and meter the cap - it will show you the ripple/noise
                  My only experience in measuring AC was to measure the house voltage. And I do not know how to measure or know the ripple/noise. But anyway, I set the meter to AC and meter the 400V cap.

                  The first meter used was a digital meter. When the power supply is connected to main and to the computer but without being switched on, I found the reading was jumping from 78 V to 0V and from then again and again about once every second. When the computer was turned on, the reading was jumping from 4X V to 0V.

                  The second meter used was also a digital meter but less than $10. When the power supply is connected to main and to the computer but without being switched on, the reading was about 370V. When the computer was turned on, the reading was 600V.

                  The third meter used was an old analogue meter. When the power supply is connected to main and to the computer but without being switched on, the reading was about 200V. When the computer was turned on, the reading was about 390V.

                  Are there any indications from the above results?

                  Comment


                    #29
                    Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                    Originally posted by tmhobadcap View Post
                    Are there any indications from the above results?
                    It's really hard to understand.
                    Either the power supply is very modern and uses AC cycle skipping to increase efficiency.
                    Or it is broken.
                    Without knowing what the control chips actually are it is impossible to go further IMO.
                    Please see this thread to get an idea what cycle skipping is:
                    https://www.badcaps.net/forum/showth...&highlight=PFC

                    Try to use a magnifying glass and read the chip numbers, it is not what you wrote in post #22, I can see that much from your photos...
                    Last edited by Per Hansson; 01-14-2023, 02:14 AM.
                    "The one who says it cannot be done should never interrupt the one who is doing it."

                    Comment


                      #30
                      Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                      Originally posted by tmhobadcap View Post
                      The part number is difficult to see. There are 3 rows. I can only see the last few numbers/characters on each row as follows.
                      02N
                      S107
                      0031
                      This is your LTA702N and here is the diagram with it.
                      Attached Files
                      Last edited by lotas; 01-14-2023, 04:26 AM.

                      Comment


                        #31
                        Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                        Originally posted by tmhobadcap View Post
                        My only experience in measuring AC was to measure the house voltage. And I do not know how to measure or know the ripple/noise. But anyway, I set the meter to AC and meter the 400V cap.

                        The first meter used was a digital meter. When the power supply is connected to main and to the computer but without being switched on, I found the reading was jumping from 78 V to 0V and from then again and again about once every second. When the computer was turned on, the reading was jumping from 4X V to 0V.

                        The second meter used was also a digital meter but less than $10. When the power supply is connected to main and to the computer but without being switched on, the reading was about 370V. When the computer was turned on, the reading was 600V.

                        The third meter used was an old analogue meter. When the power supply is connected to main and to the computer but without being switched on, the reading was about 200V. When the computer was turned on, the reading was about 390V.

                        Are there any indications from the above results?
                        the first meter makes me think the cap is bad.

                        the other 2 look like they where set to DC range.
                        very confusing.

                        Comment


                          #32
                          Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                          Cheap digital multimeters tend to give abnormally high readings if you apply DC while they're set to the AC volts range. If you measure a 9V battery on the AC range, you get 20V.

                          Comment


                            #33
                            Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                            For the AC test on the 400V cap, I am sure that I set the meters to the AC range.

                            Comment


                              #34
                              Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                              On the capacitor (400v) after the diode bridge, it is necessary to measure at a constant voltage.

                              Comment


                                #35
                                Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                                Originally posted by lotas View Post
                                On the capacitor (400v) after the diode bridge, it is necessary to measure at a constant voltage.
                                a good meter set to AC on a DC rail will display the ripple.
                                we have been using that trick to test smoothing caps for decades.

                                Comment


                                  #36
                                  Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                                  Originally posted by stj View Post
                                  a good meter set to AC on a DC rail will display the ripple.
                                  we have been using that trick to test smoothing caps for decades.
                                  It is now clear.

                                  Comment


                                    #37
                                    Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                                    Check my link in reply #29 lotas, within there I link to a Youtube video I uploaded showing AC cycle skipping in action:
                                    https://www.youtube.com/watch?v=M8ICFj07Tc0
                                    The voltage jumps from 330v to 390v back and forth.
                                    Obviously when voltage is decreasing no current is drawn from the grid so the leftmost meter shows 0w consumption.
                                    It is a way to increase efficiency.
                                    Unfortunantely I was unable to find a datasheet for the IC that you identified, so I don't know if this particular adapter supports it or not...
                                    "The one who says it cannot be done should never interrupt the one who is doing it."

                                    Comment


                                      #38
                                      Re: Please help to fix this PA-1151-03HS-ROHS power adapter

                                      efficiency at the expense of the life of the primary capacitor i suspect

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