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Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replaced

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    #1

    Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replaced

    Hello all!


    My name is ken and I have followed several threads https://www.badcaps.net/forum/showth...light=sun+24.1 and http://s807.photobucket.com/albums/y...AMSUNG%20244T/ concerning the LTM240M2 displays and problems surrounding the AC inverters. I have two identical Sun LCD's which are affected by the same problem. After examining the AC inverter board, I was able to visually confirm 3 bad 1000uf 35v capacitors. So I got a few of those from radioshack, unsoldered the bad ones, installed the new ones, reassembled the monitor, and now it doesn't even reach standby. My other display remains untouched, however it is not reaching standby power either. Neither display turns on, nor do they flash the LED to indicate status. I paid very close attention to how the displays were constructed as I disassembled and reassembled each one. As far as I can see, everything is as it was before disassembly.


    I will include several before/after shots of the AC inverter board as well as the other logic board. Please help me badcaps! I dont know what I've done wrong here since my other monitor should at least have a blinking green LED (which was the initial problem).


    PS: I noticed on the other logic board there is an AC 1501-33 IC buck booster chip. I have a multimeter but I am unsure how to probe my boards to see if they are recieving the needed voltage[s]. Thank you.

    Pictures located at http://imgur.com/a/1gTLl as well.



    Many thanks in advance!
    -Ken






    Attached Files
    Last edited by whiteboy; 10-10-2011, 03:45 PM. Reason: rearranged photos
    Tags: None
    #2
    Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

    Originally posted by whiteboy View Post
    was able to visually confirm 3 bad 1000uf 35v capacitors. So I got a few of those from radioshack, unsoldered the bad ones, installed the new ones, reassembled the monitor, and now it doesn't even reach standby.
    Radio Shack doesn't sell low ESR capacitors which are required in a SMPS application.

    In addition, Capxon are really bad capacitors (only Fuhjyuu is worse) so anything that says Capxon should also be replaced. The only exception would be the largest cap on the board. It rarely, but not never, fails.

    Suitable replacements can be ordered from digikey.com. Members prefer Panasonic FR, FM, and FC (in that order).

    So replace ALL your electrolytic capacitors on the power/inverter board and then check for 5V SB.

    Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300
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      #3
      Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

      two questions: How do I meter my monitor? How do I determine why the 2nd display (Capxon caps remain within) wont reach standby?

      Comment

        #4
        Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

        Also what IC's am I supposed to be metering?

        Comment

          #5
          Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

          Originally posted by whiteboy View Post
          two questions: How do I meter my monitor?
          In the other thread, there is a top down picture of the power board in post #1. This is our preferred view, not the angle look you have.

          On the left hand side of the power board as per picture in post #1, there is a 4 pin connector. It says 5.3V, GND, 5V SB, and something else I cannot make out.

          Make sure the monitor is plugged in.

          Put your black lead into COM, red lead into voltage. Put your multimeter to 20V DC if manual ranging. Put your black probe on the GND and your red probe on 5V SB.

          Report this reading.
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            #6
            Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

            Originally posted by whiteboy View Post
            http://s807.photobucket.com/albums/y...AMSUNG%20244T/
            Also note that budm shows the replacement caps and they are Panasonic (you can tell from the "T" vent on top). So again, your Radio Shack caps are only "general purpose" caps and not "low ESR" caps.

            Low ESR caps are required in a SMPS application.
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              #7
              Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

              Retirecaps, I believe my ac inverter board is different than the one listed @ https://www.badcaps.net/forum/showth...light=sun+24.1. Before I buy anything else I need to test my other display with the Capxcom caps to verify if its receiving power or not.



              Attached Files

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                #8
                Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

                Originally posted by whiteboy View Post
                Retirecaps, I believe my ac inverter board is different than the one listed
                Please post a picture (right side up) of the red/black connectors so we can see the legend and pin numbering.

                Also, in this top down picture, you have another bloated cap. It is just left and slightly above of the "solder direction" on the pcb.

                Before I buy anything else I need to test my other display with the Capxcom caps to verify if its receiving power or not.
                Don't order anything yet until we measure some voltages.
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                  #9
                  Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

                  Wow retirecaps, what an eye! I have 20/20 here and didn't see that ;-) Here are the requested pictures, I hope they are posted correctly:





                  The red black cables are labeled 1 & 1 - 14

                  Also tell me how I can test my caps (if possible) with my IDEAL 61-340 meter.



                  Best,
                  Ken
                  Attached Files

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                    #10
                    Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

                    Originally posted by whiteboy View Post
                    I have 20/20 here and didn't see that ;-)
                    I wish I had 20/20 vision. Unfortunately, after many years of computer use, they have degraded.

                    The red black cables are labeled 1 & 1 - 14
                    Right next to pin 14 is a ground screw. Put your board back inside the monitor and put the screw in.

                    Dial your multimeter to read DC volts.

                    Put your black probe on the ground screw by pin 14. Put your red probe on every pin on each connector. We are looking for 5.4V, 6.2V, 13V, and/or 24V (as per legend). Some will be 0V (for ground).

                    List each connector, pin, and DC V reading in some readable tabular format.

                    Also tell me how I can test my caps (if possible) with my IDEAL 61-340 meter.
                    Your multimeter can read caps up to 4000uF according to the manual. Caps have to read "out of circuit". That is, desoldered.

                    Dial your multimeter to read capacitance.

                    Put your red probe on the positive and black on the negative leg of the cap. A good cap should read close to the value stated on the sleeve. A bloated cap will read significantly less. I can already tell you that once you desoldered that small bloated cap, it will read less than the sleeve uF.

                    Remember a multimeter does not measure ESR.
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                      #11
                      Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

                      RetiredCaps,

                      I measured both monitors and here are the results


                      Monitor A (Unchanged)

                      1: 1.4v to .810v to 1.6v
                      2: 0
                      3: 0

                      1: 0
                      2: 0
                      3: 0
                      4: 0
                      5: 0
                      6: 0
                      7: 0
                      8: 0
                      9: 0
                      10: 000.1mV
                      11: 0
                      12: 0
                      13: 0
                      14: 0


                      Monitor B (4 Caps swapped)

                      1: 1.811V to 2.1V to 2.24V
                      2: 0
                      3: 0

                      1: 0
                      2: 0
                      3: 0
                      4: 0
                      5: 0
                      6: 0
                      7: 0
                      8: 0
                      9: 0
                      10: 000.1mV
                      11: 000.1mV
                      12: 0
                      13: 0
                      14: 0



                      It seems that the first pin is constantly climbing on both monitors. Each system was metered with the front bezel removed and the front panel switches unplugged. Is there anything else I should be meter?



                      Best,
                      Ken

                      Comment

                        #12
                        Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

                        btw you were correct regarding the capacitor values being altered....each 1000uF cap measured at least 1/2 of its capacitance!

                        Comment

                          #13
                          Re: Sun 24.1 LCD / Samsung 244T (LTM240M2-L03) will not power on after badcaps replac

                          Originally posted by whiteboy View Post
                          Is there anything else I should be meter?
                          1) Let's stick with the original monitor for troubleshooting. Doing this remotely is difficult enough, adding another monitor, though identical, doubles the complexity.

                          2) All the secondary 0.00 V DC indicate that the SMPS is not starting.

                          3) I'm not sure which little cap is the startup cap, but measure the DC voltage across each cap circled in red. Red probe to + and black probe to -. Report if the voltage is steady of fluctuating. We know one of the little caps is bad for sure and will definitely need to be replaced. This one cap could be the startup and sole reason why the SMPS doesn't start.

                          Report all readings and their board location/designation.

                          4) CAREFULLY, measure the DC voltage across the largest cap. Red probe to + and black probe to -. This reading could range anywhere from 165DC to 375V DC when working.
                          Attached Files
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