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    Re: Samsung Syncmaster 245BW

    Originally posted by stewart710
    After seeing the success of a few people on here, I finally pulled the LCD monitor out again that I started this thread for. Cloepula, I checked the voltage you asked about and it was 15.61v. I bought a f9222l and installed it with no change. I checked my transistor 'BR' in place and I could only get a reading in one direction with my ohmmeter.

    Speaking of the shotgun approach, I thought maybe I would get lucky replacing the f9222l, but I still only get the standby voltage. Still just the blue light special and no picture.

    Welcome back Bill!
    So, then you must change this br because in my case was the same thing, if you read with care my post you will find thet me alsow found it conductive in only one position, when change with replacment piece, there is no reading with dmm.

    Comment


      Re: Samsung Syncmaster 245BW

      You are correct. I misread that. Did you test with it in place or out of circuit?

      Thanks

      Comment


        Re: Samsung Syncmaster 245BW

        Originally posted by cloepula
        So, then you must change this br because in my case was the same thing, if you read with care my post you will find thet me alsow found it conductive in only one position, when change with replacment piece, there is no reading with dmm.

        Would this be the correct part to order: http://search.digikey.com/scripts/Dk...16794095449691

        Comment


          Re: Samsung Syncmaster 245BW

          Tested in and out of circuit, result the same.

          Comment


            Re: Samsung Syncmaster 245BW

            You can try this transistor, but maybe your controler is burned again. I first changed this br and then changed f9222L.

            Comment


              Re: Samsung Syncmaster 245BW

              Originally posted by cloepula
              You can try this transistor, but maybe your controler is burned again. I first changed this br and then changed f9222L.
              Hopefully not. I checked the voltages and while they weren't correct (probably because of the 'br' transistor), it was outputting different voltages. If it was burnt out, wouldn't there be nothing to read coming off the f9222l?

              Comment


                Re: Samsung Syncmaster 245BW

                I dont know this.

                Comment


                  Re: Samsung Syncmaster 245BW

                  Originally posted by cloepula
                  I dont know this.
                  Cloepula,

                  I finally got my F9222L parts in and replacing it did not help with the unstable
                  24V when all six inverters are connected to the backlights. There is something
                  else that is the root cause and I will need to dig in deeper to find it.
                  The "BR" transistor you mentioned on your mail is actually "BQ" on mine and I
                  believe someone else mentioned that. I was able to find a partial schematic for this power supply so it should make things a little bit easier in trying to
                  troubleshoot this. In the schematic this "BQ" transistor is marked as a
                  2SC2412 NPN transistor. It does indeed come up with this transistor when
                  searching for "BQ sot-23" on the net. Unfortunately the one on this board
                  measures ok as a transistor. I was going to use a resistive load to load one
                  of the inverter outputs such that it will the power supply will stay on. Do you
                  know how much current a typical 19 or 20 inch length backlight consumes ?
                  The 24V output is rated for 2.5A per the silkscreen on the power supply
                  board. I'm estimating each of the backlights is drawing about 300-350mA. Using 3X 1K ohm in series should get me in the ballpark. I'm expecting the
                  24V output to be stable and continue to run. We will see.

                  Comment


                    Re: Samsung Syncmaster 245BW

                    How did you manage to find a schematic of the power supply? I'm pretty sure samsung wouldn't have just emailed you a PDF if you contacted them. Or maybe they did?
                    Could you post a link?
                    If it's broken, fix it. If it's not broken, improve it.

                    Comment


                      Re: Samsung Syncmaster 245BW

                      Originally posted by Aruba
                      Cloepula,

                      I finally got my F9222L parts in and replacing it did not help with the unstable
                      24V when all six inverters are connected to the backlights. There is something
                      else that is the root cause and I will need to dig in deeper to find it.
                      The "BR" transistor you mentioned on your mail is actually "BQ" on mine and I
                      believe someone else mentioned that. I was able to find a partial schematic for this power supply so it should make things a little bit easier in trying to
                      troubleshoot this. In the schematic this "BQ" transistor is marked as a
                      2SC2412 NPN transistor. It does indeed come up with this transistor when
                      searching for "BQ sot-23" on the net. Unfortunately the one on this board
                      measures ok as a transistor. I was going to use a resistive load to load one
                      of the inverter outputs such that it will the power supply will stay on. Do you
                      know how much current a typical 19 or 20 inch length backlight consumes ?
                      The 24V output is rated for 2.5A per the silkscreen on the power supply
                      board. I'm estimating each of the backlights is drawing about 300-350mA. Using 3X 1K ohm in series should get me in the ballpark. I'm expecting the
                      24V output to be stable and continue to run. We will see.
                      This br part if is ok will not give you any reading with dmm. Will always seam like completly open

                      Comment


                        Re: Samsung Syncmaster 245BW

                        Or maybe Aruba your board is not the same like mine, and have somme other diferences. And for flickering, maybe is somme zener become a little bit weak and releasing on lower voltage then is normal to release. And check all caps with esr tester for hi esr, and with dmm for shorts.

                        Comment


                          Re: Samsung Syncmaster 245BW

                          I have 2 of these 245bw's 1 has the blue light only problem, the other is a flickerer, just found this forum, I will try to test them out

                          Comment


                            Re: Samsung Syncmaster 245BW

                            Originally posted by cloepula
                            Or maybe Aruba your board is not the same like mine, and have somme other diferences. And for flickering, maybe is somme zener become a little bit weak and releasing on lower voltage then is normal to release. And check all caps with esr tester for hi esr, and with dmm for shorts.
                            The experiment with the load worked and kept the screen on but it was still flickering. Found out that by adding a load of 0.7A or more on the 24V output
                            the flickering goes away and the 24V is stable. Once it sits like this and all
                            warmed up I can lower this current lower to about 0.2A before it will start to
                            flicker again. Some components are much more sensitive than others to the
                            freeze spray I apply to them but the area of where the 5.6V zener diode
                            (DZM803) is the most sensitive. I have tested this zener and it does test out
                            as a 5.6V zener. I do have some other 5.6V zener I can try to replace with
                            but don't have a good feeling that it will fix the problem.
                            I measure a slightly fluctuating voltage on CP803 82uF, 450V bulk cap of
                            between 356-375V and the power factor measured is only 0.65. What do you
                            measure for voltage on the bulk cap and have you measured the power
                            factor ?

                            Comment


                              Re: Samsung Syncmaster 245BW

                              Originally posted by Aruba
                              The experiment with the load worked and kept the screen on but it was still flickering. Found out that by adding a load of 0.7A or more on the 24V output
                              the flickering goes away and the 24V is stable. Once it sits like this and all
                              warmed up I can lower this current lower to about 0.2A before it will start to
                              flicker again. Some components are much more sensitive than others to the
                              freeze spray I apply to them but the area of where the 5.6V zener diode
                              (DZM803) is the most sensitive. I have tested this zener and it does test out
                              as a 5.6V zener. I do have some other 5.6V zener I can try to replace with
                              but don't have a good feeling that it will fix the problem.
                              I measure a slightly fluctuating voltage on CP803 82uF, 450V bulk cap of
                              between 356-375V and the power factor measured is only 0.65. What do you
                              measure for voltage on the bulk cap and have you measured the power
                              factor ?
                              If you check the diode and is ok, then is no need to change. How you measure power factor? And this 0.65 what is this? My monitor is returned to friend, and is in use by him, so i canot anymore make measurment on the supply board. About the unstable voltage, my board alsow have alot of unstable voltages on it before was fixed, to be onest when everithing start to work i measure just somme voltages on 5.2v ic controler, and was stable, output 5.3, 24v, and 5.2v was stable to. On this board i change a capacitor i think was 18nf 630v hi frequ, mkp. Changed it with phillips 1500v 15nf.

                              Comment


                                Re: Samsung Syncmaster 245BW

                                Originally posted by cloepula
                                If you check the diode and is ok, then is no need to change. How you measure power factor? And this 0.65 what is this? My monitor is returned to friend, and is in use by him, so i canot anymore make measurment on the supply board. About the unstable voltage, my board alsow have alot of unstable voltages on it before was fixed, to be onest when everithing start to work i measure just somme voltages on 5.2v ic controler, and was stable, output 5.3, 24v, and 5.2v was stable to. On this board i change a capacitor i think was 18nf 630v hi frequ, mkp. Changed it with phillips 1500v 15nf.
                                When using the DVM I mentioned I measure 356-375VDC on the bulk cap
                                which when working properly should be a solid voltage. I was expecting
                                somewhere between 370-400V. Today using a scope I measured this voltage
                                again and I got something totally unexpected. You can see the waveform on
                                the included picture. As you may know this monitor has a PFC (power factor
                                corrected) front end that boost the line voltage up to around 370-400VDC.
                                A TDA4863 IC from Infineon is used to accomplish this feature which when
                                working properly should present a power factor that is close to 1. Practically
                                though the achievable power factor is between 0.90 - 0.99. As when I
                                measure the power factor using a power analyzer I measured only a power
                                factor of 0.65 which tells me that the power factor correction is not
                                happening. I was not able to find anything wrong with any of the components
                                surrounding the IC so maybe the controller is at fault. Again I don't have any
                                of these IC so need to make another order.
                                For those that want to check their flickering monitors if they have the same
                                symptoms I have they can:
                                - measure the voltage across the 82uF, 450V cap and see if they also have a
                                fluctuating voltage between 356-375V.
                                - measure the 24V output and see if that fluctuates between 20-24V.
                                - use a hair dryer and heat up the area of pin7-14 of the F9222L IC and see
                                if the flickering goes away and when it cools down that the flickering
                                returns.
                                Attached Files

                                Comment


                                  Re: Samsung Syncmaster 245BW

                                  Originally posted by Aruba
                                  When using the DVM I mentioned I measure 356-375VDC on the bulk cap
                                  which when working properly should be a solid voltage. I was expecting
                                  somewhere between 370-400V. Today using a scope I measured this voltage
                                  again and I got something totally unexpected. You can see the waveform on
                                  the included picture. As you may know this monitor has a PFC (power factor
                                  corrected) front end that boost the line voltage up to around 370-400VDC.
                                  A TDA4863 IC from Infineon is used to accomplish this feature which when
                                  working properly should present a power factor that is close to 1. Practically
                                  though the achievable power factor is between 0.90 - 0.99. As when I
                                  measure the power factor using a power analyzer I measured only a power
                                  factor of 0.65 which tells me that the power factor correction is not
                                  happening. I was not able to find anything wrong with any of the components
                                  surrounding the IC so maybe the controller is at fault. Again I don't have any
                                  of these IC so need to make another order.
                                  For those that want to check their flickering monitors if they have the same
                                  symptoms I have they can:
                                  - measure the voltage across the 82uF, 450V cap and see if they also have a
                                  fluctuating voltage between 356-375V.
                                  - measure the 24V output and see if that fluctuates between 20-24V.
                                  - use a hair dryer and heat up the area of pin7-14 of the F9222L IC and see
                                  if the flickering goes away and when it cools down that the flickering
                                  returns.
                                  Why to use hairdryer and worm the space around ic?

                                  Comment


                                    Re: Samsung Syncmaster 245BW

                                    Originally posted by cloepula
                                    Why to use hairdryer and warm the space around ic?
                                    In many cases you may find that the product you are working on works
                                    better when it is "cold" meaning the components within the product
                                    has not warmed up to their usual working temperature. The time to failure could be hours before the product starts to show the failing symptom(s).
                                    A heat gun or a hair dryer will do in a pinch to warm up the area you think has a temperature sensitivity. This method is just to accelerate the heating process where otherwise you may have to wait for many hours before the
                                    symptoms appear before you can narrow the problem area. Products that
                                    works correctly do not or should I say should not have a temperature
                                    sensitivity in the typical operating range of 0-40 deg C. On the other hand
                                    for a product that has a problem only when it is "cold" you can do the opposite and try cooling the area down that has a temp sensitivity
                                    with freeze spray. These usually come in a can form and you can attach a
                                    tiny tube to it so you can direct the cold spray only to the area of concern.
                                    Using both heat gun and freeze spray in conjuction with each other you can
                                    sometimes see the symptom come and go and therfor hopefully narrow the
                                    problem down to the component(s) that is no longer operating correctly within the typical 0-40 C temp range.

                                    Comment


                                      Re: Samsung Syncmaster 245BW

                                      Originally posted by Aruba
                                      In many cases you may find that the product you are working on works
                                      better when it is "cold" meaning the components within the product
                                      has not warmed up to their usual working temperature. The time to failure could be hours before the product starts to show the failing symptom(s).
                                      A heat gun or a hair dryer will do in a pinch to warm up the area you think has a temperature sensitivity. This method is just to accelerate the heating process where otherwise you may have to wait for many hours before the
                                      symptoms appear before you can narrow the problem area. Products that
                                      works correctly do not or should I say should not have a temperature
                                      sensitivity in the typical operating range of 0-40 deg C. On the other hand
                                      for a product that has a problem only when it is "cold" you can do the opposite and try cooling the area down that has a temp sensitivity
                                      with freeze spray. These usually come in a can form and you can attach a
                                      tiny tube to it so you can direct the cold spray only to the area of concern.
                                      Using both heat gun and freeze spray in conjuction with each other you can
                                      sometimes see the symptom come and go and therfor hopefully narrow the
                                      problem down to the component(s) that is no longer operating correctly within the typical 0-40 C temp range.
                                      Ok. i never use this metod, but now i will try when have similar problem. Ty.
                                      I wait for you to solve this flickering problem.

                                      Comment


                                        Re: Samsung Syncmaster 245BW

                                        Aruba??
                                        Flickering solved or you gived up on this?

                                        Comment


                                          Re: Samsung Syncmaster 245BW

                                          I see you have an oscilloscope.
                                          This days me to bouth my first scope, is a cheap one, and second hand to, and have only one probe 10x for now. Starting to make some measurment with scope, but must buy a 100x probe, because my scope is only 20v. Picoscope adc200/50. 25mhz. For starting and investigating on 100khz smps power supply i think will be good anough. Can you give me somme advice on this?

                                          Comment

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