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    Samsung 245BW No 24V or5.3V has good stand by

    I would like to start a new thread on this, See if someone can help me figure out why I have no 24V or 5.3V outputs
    What I know,
    All of the Electrolytic Caps have been replaced, with good quality low ESR
    I have 391V DC across the large capacitor
    I have a good stand by voltage of 5.2 V
    When the front power button is pushed I see a PS on voltage of 3.2V
    There is no 24V 0r 5.3V noticed on the power supply.
    I have given the P/S a good looking over; nothing is jumping out as being faulty.
    From some of the other threads on this monitor I think the F9222L controller is responsible for starting the 24V.
    These are the readings I get on the pins of F9222L referenced with pin 8 as ground
    Pin 4=0V Pin 7= 19.54V Pin 10= 4.94V
    Pin 11=4.6V Pin 12=4.94V Pin 13= 3.03V
    Pin 14=.7V Pin15=4.93V Pin16=.011V and
    Pin23= 391V
    I have attached a schematic from another thread that is of the power supply I am working on.
    Attached Files
    Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

    #2
    Re: Samsung 245BW No 24V or5.3V has good stand by

    This is a VERRRRY interesting circuit. I see a couple of points to consider.

    1. The nominal output voltage of the PFC circuit would appear to be 292 volts.

    2. When PSON goes high it turns on both the PFC controller (TDA4863G pin 8) and the Main SMPS controller (F9222L pin 7).

    3. DZT851 and DZT852 for a protection circuit.

    I'd check the PFC output voltage when the power supply is supposed to be off, then check VCC at the F9222L.

    PlainBill
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

    Comment


      #3
      Re: Samsung 245BW No 24V or5.3V has good stand by

      Originally posted by PlainBill View Post
      This is a VERRRRY interesting circuit. I see a couple of points to consider.

      1. The nominal output voltage of the PFC circuit would appear to be 292 volts.

      2. When PSON goes high it turns on both the PFC controller (TDA4863G pin 8) and the Main SMPS controller (F9222L pin 7).

      3. DZT851 and DZT852 for a protection circuit.

      I'd check the PFC output voltage when the power supply is supposed to be off, then check VCC at the F9222L.

      PlainBill
      Ok,I measured across the Big cap again, monitor on 392V. Monitor off 154V
      Pin 8 of TDA4863G is 392V on,and154V off
      VCC pin 7 of F9222L is 19.62 on and 0V monitor off
      Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

      Comment


        #4
        Re: Samsung 245BW No 24V or5.3V has good stand by

        Frankly, the likely suspect is the F9222L. Most voltages are close, the only one that isn't is pin 11, the Comp input, and the reading you got indicates the output voltage is low.

        If you are reluctant to order one, I understand. I notice there are 3 bipolar transistors, 5 conventional diodes, and 3 zener diodes on the primary side, and of course the two dual diodes on the secondary. If those are not shorted, my suggestion would be to replace the F9222L. I cannot come up with a definitive test to show if that is or is not the problem.

        PlainBill
        For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

        Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

        Comment


          #5
          Re: Samsung 245BW No 24V or5.3V has good stand by

          Fortunately, you have a lot of information given on that schematic. My first question is why you replaced all the capacitors? Did your ESR meter indicate that any caps were faulty? Locating a faulty part can give you clues to other failed circuit parts, so that just doesn't make sense to me. You do not have any 5.3v output, because the 5.3v circuit depends upon having the 24v input to operate. So the problem is actually that the switched 24v supply is not working. Voltages on the switching IC F9222 don't look unusual considering that the supply isn't running. A short in the 5.3v switching IC could kill the whole sw. 24 volt supply, however.

          It isn't clear to me that the main supply is ok. You say that you have 392v at the input of the sw 24v supply, but only 292v is specified. (I'm assuming you mean CP803?).

          First, take a resistance reading (power off) from sw. 24v to ground. You could also disconnect the +24 output. I'd use a dvm to test DZM803, the switchers, and other semis in the primary. Also check the diode packs on the secondary and do an ESR check on the secondary filters. Then if nothing suspicious comes up, I'd have a look at the + end of CM851 with a scope just at the moment you turn the supply on. That will give you something to go on. You might in fact have a bad F9222. But if your resistance readings across pins 4,19 and 20,23 don't show shorts, I'd look around a little more first.
          Is it plugged in?

          Comment


            #6
            Re: Samsung 245BW No 24V or5.3V has good stand by

            Originally posted by Longbow View Post

            It isn't clear to me that the main supply is ok. You say that you have 392v at the input of the sw 24v supply, but only 292v is specified. (I'm assuming you mean CP803?).
            That confused me, too. Notice the table inset in the schematic. 392 volts appears to be correct.

            PlainBill
            For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

            Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

            Comment


              #7
              Re: Samsung 245BW No 24V or5.3V has good stand by

              Sorry to say, I do not have an ESR meter or an oscilloscope.
              If you look at the schematic it lists what I would guess are known good voltages, and it dose list 391V on pin of F9222L.
              I haven't given up on this yet and I will try some of your suggestions.
              Thank you.
              Attached Files
              Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

              Comment


                #8
                Re: Samsung 245BW No 24V or5.3V has good stand by

                I reading through all the other threads, it appears there may have been a problem with QM802
                Any ideas what type of voltages I would see on it?
                Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                Comment


                  #9
                  Re: Samsung 245BW No 24V or5.3V has good stand by

                  Originally posted by alexanna View Post
                  I reading through all the other threads, it appears there may have been a problem with QM802
                  Any ideas what type of voltages I would see on it?
                  Analyze the circuit!!! (Yes, it's a strange one.)

                  Pins 10 and 15 are at 5 volts. RM810 and RM811 form a voltage divider, so the junction of them with RM812 should be at 3.3 volts EXCEPT the base-emitter junction is biased on. Since RM812 is only 4.7K that will reduce the voltage somewhat. Still, the emitter of QM802 will read 0 volts, the base should read .7 volts, and the collector will read 0 volts!!!

                  PlainBill
                  For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                  Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                  Comment


                    #10
                    Re: Samsung 245BW No 24V or5.3V has good stand by

                    Originally posted by PlainBill View Post
                    Analyze the circuit!!! PlainBill
                    Well I've been trying to, Have you ever heard the saying. I'm up to my ass in alligators and just learning how to swim?
                    Qm802 looks like it's working correctly.
                    I have noticed a few discrepancies in the schematic, off of pin 10 of F922l DM801 is not there.
                    If you follow Pin 19 from FL9222l there is a DM801 in the circuit.
                    Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                    Comment


                      #11
                      Re: Samsung 245BW No 24V or5.3V has good stand by

                      Originally posted by alexanna View Post
                      Well I've been trying to, Have you ever heard the saying. I'm up to my ass in alligators and just learning how to swim?
                      Not exactly. I've heard "When you are up to your ass in alligators, it's hard to remember you objective was to drain the swamp." And "If you plan on swimming with the sharks, take steps to avoid being eaten." And let's not forget "When learning to swim, it's best to start in a shallow pool." None of which helps with the immediate problem.

                      Originally posted by alexanna View Post
                      Qm802 looks like it's working correctly.
                      I have noticed a few discrepancies in the schematic, off of pin 10 of F922l DM801 is not there.
                      If you follow Pin 19 from FL9222l there is a DM801 in the circuit.
                      Is that a typo on the schematic, or is there no diode present?

                      PlainBill
                      For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                      Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                      Comment


                        #12
                        Re: Samsung 245BW No 24V or5.3V has good stand by

                        QM802 might be a startup circuit, since it is set up to pulse QM803 low after a delay controlled by CM809. Can't find any info on the F9222L; looks like a proprietary Samsung part. I've never seen anything quite like this. In any case, I would take the resistance measurements around the secondary, after first confirming that your switching FET's are not shorted. I see a number of complaints about this supply posted in various places, but no answers. Looks like you've got the job!! In an attempt at humor, maybe forum registration should require the purchase of an ESR meter? (hint, hint)
                        Is it plugged in?

                        Comment


                          #13
                          Re: Samsung 245BW No 24V or5.3V has good stand by

                          Originally posted by PlainBill View Post
                          Is that a typo on the schematic, or is there no diode present?

                          PlainBill
                          The diode and transistor off of pin 10 of F9222L shown on the schematic are not on the board.
                          The transistor they list on the schematic as QM803 is also not there.
                          My initial checks of all of the transistors are not indicating any shorts.
                          And all voltage testing has been done with the inverter and LCD panel connected, and then again disconnected.
                          As soon as I can get the gray matter going again, I will verify everything one more time.
                          Last edited by alexanna; 06-28-2011, 11:21 AM. Reason: removed ref to capacitor for QM803
                          Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                          Comment


                            #14
                            Re: Samsung 245BW No 24V or5.3V has good stand by

                            Originally posted by Longbow View Post
                            QM802 might be a startup circuit, since it is set up to pulse QM803 low after a delay controlled by CM809. Can't find any info on the F9222L; looks like a proprietary Samsung part. I've never seen anything quite like this. In any case, I would take the resistance measurements around the secondary, after first confirming that your switching FET's are not shorted. I see a number of complaints about this supply posted in various places, but no answers. Looks like you've got the job!! In an attempt at humor, maybe forum registration should require the purchase of an ESR meter? (hint, hint)
                            I am not noticing any shorted FETs
                            Every monitor I get is at least 3 years old, and they all get a total recap, no exceptions
                            Next purchase on my list is going to be an oscilloscope
                            Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                            Comment


                              #15
                              Re: Samsung 245BW No 24V or5.3V has good stand by

                              Originally posted by Longbow View Post
                              QM802 might be a startup circuit, since it is set up to pulse QM803 low after a delay controlled by CM809. Can't find any info on the F9222L; looks like a proprietary Samsung part. I've never seen anything quite like this. In any case, I would take the resistance measurements around the secondary, after first confirming that your switching FET's are not shorted. I see a number of complaints about this supply posted in various places, but no answers. Looks like you've got the job!! In an attempt at humor, maybe forum registration should require the purchase of an ESR meter? (hint, hint)
                              It's not a proprietary Samsung part. It was a standard Fuji part, introduced about 5 years ago. Even rudimentary technical specs are available. A detailed original datasheet is much harder to find.

                              PlainBill
                              For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                              Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                              Comment


                                #16
                                Re: Samsung 245BW No 24V or5.3V has good stand by

                                Have you tried checking CM802? It's a 18nf 630V cap that's given other's a problem.

                                Comment


                                  #17
                                  Re: Samsung 245BW No 24V or5.3V has good stand by

                                  Originally posted by jetadm123 View Post
                                  Have you tried checking CM802? It's a 18nf 630V cap that's given other's a problem.
                                  Yea, I just read that in the other 245 thread.
                                  That was mentioned as being a problem; I don't know how I missed it.
                                  My meter is able to read from 1NF to 9999UF and it looks like its reading totally open.
                                  There are no obvious burn or bulge marks on it.
                                  I have gone through all my parts boards and I'm not finding any thing I can use.
                                  I should be able to pick one up tomorrow, I'll keep everyone informed.
                                  Thanks
                                  Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                                  Comment


                                    #18
                                    Re: Samsung 245BW No 24V or5.3V has good stand by

                                    Originally posted by PlainBill View Post
                                    :It was a standard Fuji part, introduced about 5 years ago. Even rudimentary technical specs are available. A detailed original datasheet is much harder to find. PlainBill
                                    Thanks, I was hoping that a block diagram of what's inside might help to figure out what starts and runs the internal oscillator on this chip. I'm assuming that if a supply uses a complex chip like this, it has an internal oscillator and does not depend upon a pulse from the transformer to get things going.

                                    Since the FET switchers are not shorted, I'll bet the chip itself is OK. CM802 is an excellent suggestion - the snubber network. The 18 nF value is important, just as a reminder. Also check the 1M resistor across it. A quick leakage test for CM802: pull up the transformer leg of CM802 and RM802. Power up and measure the voltage on the loose end of CM802 (to ground).
                                    Is it plugged in?

                                    Comment


                                      #19
                                      Re: Samsung 245BW No 24V or5.3V has good stand by

                                      After replacing CM802 18NF 630v volt capacitor, I have a working monitor.
                                      The part to check was identified in the other 245BW thread, I just missed it.
                                      I haven't really been working on monitors all that long, although I have repaired quite a few.
                                      What I have noticed on this type of capacitor there is usually some indication [Bulging or burnt} of a problem, Not on this one.
                                      It's something that should be checked on this monitor if the 24V is not working.
                                      Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                                      Comment


                                        #20
                                        Re: Samsung 245BW No 24V or5.3V has good stand by

                                        Congrats on the fix! Previously I called this part the snubber cap, but now I'm not so sure of the correct name. Usually the snubber network is accross the switcher primary, but this cap is in series with the coil, so all switching current flows through it. Anyway, snubber cap or tuning cap - whatever its called - is an important part in any monitor. I've seen lots of bad ones across the board, so to speak.
                                        Is it plugged in?

                                        Comment

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