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Benq G2255 doesn't power on - amber power light when plugged in

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    #41
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Did you look at my pictures on post 39 that I clearly marked where GNDs are?
    Again, look at the left side of R802, it is connected to GND.
    C805 is also connected in parallel with R802, the right side of R802/C805 are connected to pin 7 of the IC, so I do not see how you can say that one end of R802 is connected to pin 4!
    Your picture here https://www.badcaps.net/forum/attach...6&d=1515675227
    Clearly show the reading of 0.09V at TWO PLACES, both if them are GNDs. I do not see any arrow pointing to pin 4 at all.
    See my new pix that I have marked again.
    It looks like I am getting wrong DATA from you.
    Are you sure you count the IC pins correctly or may be we are not looking at the same pictures same board?
    Attached Files
    Last edited by budm; 01-11-2018, 10:58 PM.
    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


      #42
      Re: Benq G2255 doesn't power on - amber power light when plugged in

      Hello Budm,

      I'm sorry, I am still learning at this stage and your drawing makes it pretty clear what is ground and what is not. I was measuring the right pins, on the pins themselves.

      I have attached annotated photos for the opposite side of the resistors to 5V and the voltages I get on the pins. I also measured the voltage on that point in Will62's photo for reference.

      Please bear with me, I promise to listen and try and understand the first time

      Many thanks for your help and guidance.
      Attached Files

      Comment


        #43
        Re: Benq G2255 doesn't power on - amber power light when plugged in

        So at this point pin 4 (EN) does not look like it is being use to turn inveter circuit on/off like as shown in the circuit.
        The two control signal lines seem to be going to pin 7 and pin 8.
        May be you have to trace out and see if pin 4 is connected to anything else beside C802.
        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


          #44
          Re: Benq G2255 doesn't power on - amber power light when plugged in

          I'm going to throw in a few notes:

          1. You measured 5.5v on pin 1 (OV2). From the datasheet: "If the voltage at OV2 is always above 4.9V, the controller will treat this as a short circuit condition after a certain delay. The Fault Timer will
          start ramping up."

          2. In order to use external PWM dimming (pin 8), pin 7 must be pulled high
          first. Is it possible that JW8 is covering 2 bases? Pulling pin 7 high, as well as activating pin 4 (enable).

          3. It is possible that the solder point next to pin 4 is over a via to a sublayer
          track that you can't follow. With power off, you could use your meter (resistance) to find where the track resurfaces.

          4. A little odd that you measured 0v on pin 5. Over 1.2v is supposed to indicate that a fault has tripped the protection circuit. Shorting pin 5 to ground, bypasses the chip's protection circuit. (I would get Budm's advice before trying that.)
          Attached Files

          Comment


            #45
            Re: Benq G2255 doesn't power on - amber power light when plugged in

            It is single layer board so that is just a pad for test point.
            I sure like to get the correct diagram, I am sure we can bypass the protection circuit but I do not really want to do that but we may have to to do the test.
            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


              #46
              Re: Benq G2255 doesn't power on - amber power light when plugged in

              Has anyone ever purchased an S.M. from this site?

              http://www.service-manual.net/ashop/...?product=56211

              You might spend the $13, and get something generic, or similar to
              what you've found for free.


              Edit: Also, with power off, please check resistance between pin 4 and pin 7. There may be a trace under the chip. Thanks
              Last edited by will62; 01-12-2018, 02:19 PM.

              Comment


                #47
                Re: Benq G2255 doesn't power on - amber power light when plugged in

                So the voltage at C801 is ~20V and at pin9 is 15,5V. What resistance is R804?
                Check Q808 in diode mode for shorts.

                Comment


                  #48
                  Re: Benq G2255 doesn't power on - amber power light when plugged in

                  Originally posted by will62 View Post
                  Has anyone ever purchased an S.M. from this site?

                  http://www.service-manual.net/ashop/...?product=56211

                  You might spend the $13, and get something generic, or similar to
                  what you've found for free.


                  Edit: Also, with power off, please check resistance between pin 4 and pin 7. There may be a trace under the chip. Thanks

                  Yep, I wonder if there is trace on pin 4 that goes under the IC.
                  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


                    #49
                    Re: Benq G2255 doesn't power on - amber power light when plugged in

                    Originally posted by budm View Post
                    [/I][/B]
                    Yep, I wonder if there is trace on pin 4 that goes under the IC.
                    I tried to find a trace from pin 4, but it doesn't seem connected to anything, not even pin 7 which gives me 47 kohms resistance. Here is a picture with a light under the board.

                    So the voltage at C801 is ~20V and at pin9 is 15,5V. What resistance is R804?
                    Check Q808 in diode mode for shorts.
                    Dumah, not sure what you mean by this. I have a diode mode, but I check from wich pin to which pin and how do I see if there is a short? I tried reading from pin 4 to pin 5 (red on pin 4), pin 4 to pin 6, pin 4 to pin 7, pin 4 to pin 8 and and I get 1.5V reading in diode mode on all those pins. If I reverse my probes, I get from pin 4 to 5 and 4 to 6 - 0V, and from pin 4 to 7 and 4 to 8 - .75V???
                    Attached Files

                    Comment


                      #50
                      Re: Benq G2255 doesn't power on - amber power light when plugged in

                      I look real close at the pictures of the IC, the P/N as printed on the body is MP10091ES which I believe it is not the same as MP1009.
                      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


                        #51
                        Re: Benq G2255 doesn't power on - amber power light when plugged in

                        Originally posted by budm View Post
                        I look real close at the pictures of the IC, the P/N as printed on the body is MP10091ES which I believe it is not the same as MP1009.
                        You are right, here is everything that is written on the IC:
                        MPS 1202
                        MP10091ES
                        BB845488A

                        Comment


                          #52
                          Re: Benq G2255 doesn't power on - amber power light when plugged in

                          Hello Rddube,
                          That last pic really cleared up the trace routes. Can you take another with
                          the light further back, so that we can see the traces all the way to the back light connectors and the ap9962?

                          I'm including a pic that might help you check the ap9962. It's usually best to check them out of circuit, but you can try it and if you get weird results, just
                          unsolder the gate/source side, lift it slightly and retest.

                          Not sure what to think about pin 4 going nowhere. Most circuits that I've been
                          able to find using that chip, have the enable coming from the main board. Maybe default is enabled, until it is pulled low. It may be low now due to internal fault detection. (Have you ever checked to make sure that C802 is not shorted to ground?)
                          Attached Files

                          Comment


                            #53
                            Re: Benq G2255 doesn't power on - amber power light when plugged in

                            Originally posted by will62 View Post
                            Hello Rddube,
                            That last pic really cleared up the trace routes. Can you take another with
                            the light further back, so that we can see the traces all the way to the back light connectors and the ap9962?

                            I'm including a pic that might help you check the ap9962. It's usually best to check them out of circuit, but you can try it and if you get weird results, just
                            unsolder the gate/source side, lift it slightly and retest.

                            Not sure what to think about pin 4 going nowhere. Most circuits that I've been
                            able to find using that chip, have the enable coming from the main board. Maybe default is enabled, until it is pulled low. It may be low now due to internal fault detection. (Have you ever checked to make sure that C802 is not shorted to ground?)
                            Thanks Will, here is another pic. Checked C802 and left side is to ground and right side to ground I get 1.4K ohm.

                            In the pic you include what does 0L mean? Do I set my meter on diode for all tests, because at one point it says I should get low ohm?

                            Also, I have some AF4910N rated at 30V which is similar to the AP9962 which is rated at 40V, do you think I could try and substitute?
                            Attached Files
                            Last edited by rddube; 01-12-2018, 10:07 PM.

                            Comment


                              #54
                              Re: Benq G2255 doesn't power on - amber power light when plugged in

                              OK then MP10091... Pin 7 is enable.

                              Rddube: OL: open line/over limit. depends who you ask.
                              sorry, low reading, not ohms.



                              On the 30v part, not sure, need Budm's input there. You get a voltage spike
                              at cutoff. I haven't recognized any snubbing circuit to bring that down. You
                              can always try it.
                              Attached Files
                              Last edited by will62; 01-12-2018, 10:14 PM.

                              Comment


                                #55
                                Re: Benq G2255 doesn't power on - amber power light when plugged in

                                Originally posted by will62 View Post
                                OK then MP10091... Pin 7 is enable.

                                Rddube: OL: open line/over limit. depends who you ask.
                                sorry, low reading, not ohms.



                                On the 30v part, not sure, need Budm's input there. You get a voltage spike
                                at cutoff. I haven't recognized any snubbing circuit to bring that down. You
                                can always try it.
                                Man, I have been searching for the MP10091ES schematic, MP10091ES circuits and nothing really come up, nothing for the spec sheet either. Do you have the link where you get that from?
                                Finally clear out the confusion about the pin 4 of the IC. I am glad I took a closer look at the P/N of the IC.
                                Last edited by budm; 01-12-2018, 10:52 PM.
                                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


                                  #56
                                  Re: Benq G2255 doesn't power on - amber power light when plugged in

                                  The power MOSFET, you just check the resistance between S and D pin, since it is dual MOSFET so you will test resistance between S1 and D1, S2 and D2. it should show high resistance.
                                  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


                                    #57
                                    Re: Benq G2255 doesn't power on - amber power light when plugged in

                                    Yes, glad you caught that Budm.

                                    The schematic is from a Philips 22" that uses the chip.

                                    pdf

                                    Comment


                                      #58
                                      Re: Benq G2255 doesn't power on - amber power light when plugged in

                                      Originally posted by budm View Post
                                      The power MOSFET, you just check the resistance between S and D pin, since it is dual MOSFET so you will test resistance between S1 and D1, S2 and D2. it should show high resistance.
                                      Ok, did some tests in circuit for the power Mosfet. From S1 to D1 (there are 2 D1's) i get varying results, sometimes .5 MegaOhm, other times 47K and other times 475K ??? Same for S2 to both of the D2's.

                                      However if I measure S2 to either of the D1's I get 1 ohm, meaning a short?

                                      Should I remove the Mosfet (which will need hot air, I can do that) to test it?

                                      I'm confused but sure am glad to have you gentlemen (Budm, Will62 and Dumah) looking over my shoulder! Thanks to you so much!!

                                      PS - don't forget that this is the Power Mosfet for which I had mentionned in a previous post (#20) that there seems to be some heat marks under that chip, please see photo:

                                      https://www.badcaps.net/forum/attach...4&d=1515532125
                                      Last edited by rddube; 01-13-2018, 07:47 AM.

                                      Comment


                                        #59
                                        Re: Benq G2255 doesn't power on - amber power light when plugged in

                                        Hello again gentlemen,

                                        I said I had some AF4910N, they are installed on another scrap power board that I have and I tried removing one with hot air - what a mess.

                                        The chips (there are 4, now 3 left) are covered with this transparent glue that I have never seen before which doesn't seem to melt when I heat it up. I put my hot air at 400F and I actually pulled the traces of the board off with the glue still holding them down. I think the chip is cooked.

                                        Any idea how I can remove that glue before attempting the removal of the chip? Is 400F too high?

                                        I didn't touch the power mosfet on my monitor power board. Only did some readings that I mention in the previous post.

                                        Comment


                                          #60
                                          Re: Benq G2255 doesn't power on - amber power light when plugged in

                                          When testing in circuit, you're dealing with other components in parallel. As Budm mentioned earlier, if you don't have a short between D and S, the chip is probably fine.
                                          Look at the dual mosfet in the circuit pic in post #54. See how pin 7 is tied to pin 3? That's why you are getting a low ohms reading between D1 and S2.

                                          On removing the chips, are you applying flux before heating? You should see the solder go soft when it's ready to lift. I would think the adhesive is softening by that time. You may need to pry beneath the chip to coax it. You can also lift each pin one at a time by using a dental pick (or similar) under the pin, as you heat the pin with your soldering iron. You don't need to lift much, a mm will do.

                                          Now that we have a good pinout of the MP10091, can you go around and take voltage readings for each pin? An earlier reading that you took on pin 1, indicated a short circuit fault. I would like to see what the other voltages are. Also, somewhere along the line, you are going to need to check all caps for shorts, and resistors for open. I'll defer to Budm on what to try beyond that.
                                          Last edited by will62; 01-13-2018, 10:20 AM.

                                          Comment

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