Announcement

Collapse
No announcement yet.

Acer B326HUL power supply dead

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Acer B326HUL power supply dead

    Display only blinks and than stays dead. Check open the PSU revealed it is dead.

    There are three output rails: winding to feed the TEA1791T synchronnous rectification controller (this thing has no connection with primary side!), the output for the rectification transistor - this rail feeds the signal board, and than backlight rail.

    Seems like the unit only pumps few cycles to the secondary so voltage rises a bit and than falls down as the caps discharge. I have about 15.5 V on a small cap on the primary auxiliary rail just after the diode which slowly falls, pumps again to 15.5 V and that repeats.

    There is however oscillating voltage between like 18 and 19.6 V on the cap directly in front of the primary common PFC/PWM controller. Do not think this is normal condition. Cannot identify the controller right now, it has layer of lackquer, gonna have to try removing it.

    I do see only 320V on the input cap though, there is no spike suggesting the PFC would be turning on, so maybe the problem lays in here?
    Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

    Exclusive caps, meters and more!
    Hardware Insights - power supply reviews and more!

    #2
    Re: Acer B326HUL power supply dead

    It's very difficult to read anything in here but it seems like the PFC/quasi-resonant flyback controller is NXP, possibly TEA1751T. According to the datasheet, the startup voltage is 21-23 V so when it's at 18-19.6 that's too low.

    The path goes from the auxiliary winding on primary side through inductor to an SMD diode, capacitor and than there is "K415 C200" TO-92 bipolar transistor. The 15V feed leads to its collector, the oscillating 18-19.6V output is on its emitter. Collector and base has 1002 SMD resistor in between and base is also connected through an SMD zener to return.

    So it seems like some amplifier with zener feedback? And this is to feed the Vcc of the controller.
    Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

    Exclusive caps, meters and more!
    Hardware Insights - power supply reviews and more!

    Comment


      #3
      Re: Acer B326HUL power supply dead

      Originally posted by Behemot View Post
      It's very difficult to read anything in here but it seems like the PFC/quasi-resonant flyback controller is NXP, possibly TEA1751T. According to the datasheet, the startup voltage is 21-23 V so when it's at 18-19.6 that's too low.

      The path goes from the auxiliary winding on primary side through inductor to an SMD diode, capacitor and than there is "K415 C200" TO-92 bipolar transistor. The 15V feed leads to its collector, the oscillating 18-19.6V output is on its emitter. Collector and base has 1002 SMD resistor in between and base is also connected through an SMD zener to return.

      So it seems like some amplifier with zener feedback? And this is to feed the Vcc of the controller.
      I also have a dead power board, did you manage to find some datasheet, schematics, wathever informations about this card? Thanks

      Comment


        #4
        Re: Acer B326HUL power supply dead

        If we can see some good clear pictures of the boards and how they are connected together, that will be a good starting point.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment


          #5
          Re: Acer B326HUL power supply dead






          If you need more detailled pictures or anything else, ask.

          Thanks

          Comment


            #6
            Re: Acer B326HUL power supply dead

            Originally posted by budm View Post
            If we can see some good clear pictures of the boards and how they are connected together, that will be a good starting point.
            Is it useful?

            Thanks

            Comment


              #7
              Re: Acer B326HUL power supply dead

              SO, what Voltages do you have on that white connector of the power supply board that goes to the logic/main board?
              Never stop learning
              Basic LCD TV and Monitor troubleshooting guides.
              http://www.badcaps.net/forum/showthr...956#post305956

              Voltage Regulator (LDO) testing:
              http://www.badcaps.net/forum/showthr...999#post300999

              Inverter testing using old CFL:
              http://www.badcaps.net/forum/showthr...er+testing+cfl

              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
              http://s807.photobucket.com/user/budm/library/

              TV Factory reset codes listing:
              http://www.badcaps.net/forum/showthread.php?t=24809

              Comment


                #8
                Re: Acer B326HUL power supply dead

                Originally posted by budm View Post
                SO, what Voltages do you have on that white connector of the power supply board that goes to the logic/main board?
                Hi, Budm

                Thanks for your answer

                I have no light on the front power push button.

                I tested the general 220v power switch on the back, and the fuse.

                And to answer your question, I have 0v on each wire on the white connector, with the board plugged or unplugged:

                https://www.youtube.com/watch?v=8uVT8g2OchQ


                I have 335Vdc arriving to the "120uF / 450V" capacitor, and I unsoldered it and tested it too:

                https://www.youtube.com/watch?v=IL7uwboCR70


                Hope I done everything right, and made myself understood, English is not my first language.

                Thanks

                Comment


                  #9
                  Re: Acer B326HUL power supply dead

                  In your picture #2 on the bottom left, there is an IC (18-PIN?) there, can you read the P/N?
                  Never stop learning
                  Basic LCD TV and Monitor troubleshooting guides.
                  http://www.badcaps.net/forum/showthr...956#post305956

                  Voltage Regulator (LDO) testing:
                  http://www.badcaps.net/forum/showthr...999#post300999

                  Inverter testing using old CFL:
                  http://www.badcaps.net/forum/showthr...er+testing+cfl

                  Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                  http://s807.photobucket.com/user/budm/library/

                  TV Factory reset codes listing:
                  http://www.badcaps.net/forum/showthread.php?t=24809

                  Comment


                    #10
                    Re: Acer B326HUL power supply dead

                    Hi, I tried to take pictures and read the part references



                    n°1 : NXP TEA1751T CDX12104 TXD14241

                    n°2 : MPS1431 MP3398 E44H2168A

                    n°3 : unreadable, but seems to be the same as n°2

                    thanks

                    Comment


                      #11
                      Re: Acer B326HUL power supply dead

                      Originally posted by fred41 View Post
                      Hi, I tried to take pictures and read the part references



                      n°1 : NXP TEA1751T CDX12104 TXD14241

                      n°2 : MPS1431 MP3398 E44H2168A

                      n°3 : unreadable, but seems to be the same as n°2

                      thanks
                      OK, #1 is the one we need to find out if it has DC Voltage between VCC pin and Gnd for it run or not. Please see the spec sheet.
                      NOTES: You will be working in the HOT DEADLY side of the circuit so do not touch ANYTHING with your hands or body, you should at least plug the monitor into GFCI outlet.
                      Attached Files
                      Never stop learning
                      Basic LCD TV and Monitor troubleshooting guides.
                      http://www.badcaps.net/forum/showthr...956#post305956

                      Voltage Regulator (LDO) testing:
                      http://www.badcaps.net/forum/showthr...999#post300999

                      Inverter testing using old CFL:
                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                      http://s807.photobucket.com/user/budm/library/

                      TV Factory reset codes listing:
                      http://www.badcaps.net/forum/showthread.php?t=24809

                      Comment


                        #12
                        Re: Acer B326HUL power supply dead

                        Originally posted by budm View Post
                        OK, #1 is the one we need to find out if it has DC Voltage between VCC pin and Gnd for it run or not. Please see the spec sheet.
                        NOTES: You will be working in the HOT DEADLY side of the circuit so do not touch ANYTHING with your hands or body, you should at least plug the monitor into GFCI outlet.
                        Thanks a loot for your answer, but I'm not sure what GFCI means exactly, is it an outlet with ground? I live in France , and this is the default wall outlet we have :



                        Am I right for where to test?

                        Last edited by fred41; 05-16-2018, 11:56 AM.

                        Comment


                          #13
                          Re: Acer B326HUL power supply dead

                          GFCI means Ground Fault Circuit Interrupter. This is an electrical outlet with Reset button and a Test button on it that should a shock hazard be detected it would switch the supply to the receptacle OFF.

                          Comment


                            #14
                            Re: Acer B326HUL power supply dead

                            Originally posted by Andrew F. Ali View Post
                            GFCI means Ground Fault Circuit Interrupter. This is an electrical outlet with Reset button and a Test button on it that should a shock hazard be detected it would switch the supply to the receptacle OFF.
                            Like this?



                            I have one

                            Comment


                              #15
                              Re: Acer B326HUL power supply dead

                              This is how our electrical GFCI outlets look like. The RED button is the RESET and the BLACK button is the TEST. So is a fault is detected the RED button pops up and disconnects the supply and to reset is to just push it back in. When the Test button is depressed the RESET button pops up and so we know the system is working.
                              Attached Files

                              Comment


                                #16
                                Re: Acer B326HUL power supply dead

                                EURO GFCI outlet:
                                http://internationalconfig.com/icc6.asp?item=4721-10HG2
                                Never stop learning
                                Basic LCD TV and Monitor troubleshooting guides.
                                http://www.badcaps.net/forum/showthr...956#post305956

                                Voltage Regulator (LDO) testing:
                                http://www.badcaps.net/forum/showthr...999#post300999

                                Inverter testing using old CFL:
                                http://www.badcaps.net/forum/showthr...er+testing+cfl

                                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                http://s807.photobucket.com/user/budm/library/

                                TV Factory reset codes listing:
                                http://www.badcaps.net/forum/showthread.php?t=24809

                                Comment


                                  #17
                                  Re: Acer B326HUL power supply dead

                                  Originally posted by fred41 View Post
                                  Thanks a loot for your answer, but I'm not sure what GFCI means exactly, is it an outlet with ground? I live in France , and this is the default wall outlet we have :



                                  Am I right for where to test?
                                  That is correct pin out for TEA1751:
                                  Pin 1 = VCC
                                  Pin 2 = GND
                                  Never stop learning
                                  Basic LCD TV and Monitor troubleshooting guides.
                                  http://www.badcaps.net/forum/showthr...956#post305956

                                  Voltage Regulator (LDO) testing:
                                  http://www.badcaps.net/forum/showthr...999#post300999

                                  Inverter testing using old CFL:
                                  http://www.badcaps.net/forum/showthr...er+testing+cfl

                                  Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                  http://s807.photobucket.com/user/budm/library/

                                  TV Factory reset codes listing:
                                  http://www.badcaps.net/forum/showthread.php?t=24809

                                  Comment


                                    #18
                                    Re: Acer B326HUL power supply dead

                                    Originally posted by budm View Post
                                    Thanks budm

                                    Comment


                                      #19
                                      Re: Acer B326HUL power supply dead

                                      Originally posted by budm View Post
                                      OK, #1 is the one we need to find out if it has DC Voltage between VCC pin and Gnd for it run or not. Please see the spec sheet.
                                      NOTES: You will be working in the HOT DEADLY side of the circuit so do not touch ANYTHING with your hands or body, you should at least plug the monitor into GFCI outlet.
                                      I measured 18.5Vdc - 19Vdc

                                      And I didn't blew up the house, nor I burned myself...

                                      Thanks everyone

                                      Comment


                                        #20
                                        Re: Acer B326HUL power supply dead

                                        Hi fred41, you and I seem to be in a similar fix. I have a Benq 32" with a dead psu and the board is similar to yours. Also the fault on mine seems to be in the same general area as yours (around the TEA1751)
                                        Could you please tell me the value of the resistor on your board between pin 16 on the TEA1751 and the transformer? Mine has burnt out.
                                        Have you had any luck getting yours going?

                                        Here's my thread: https://www.badcaps.net/forum/showth...830#post890830
                                        Attached Files
                                        Last edited by the.norbulus; 04-15-2019, 10:00 AM.

                                        Comment

                                        Working...
                                        X