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    #1

    CTX S762G - Some Questions...

    Hey everyone, first-time poster here (and a bit of a novice when it comes to the electrical-speak, so take it slow ).

    Okay, so I received a CTX S762G 19" LCD monitor from work that was having a power issue. It was doing the common blinking of the LED light and would not come on. I was able to get the "Signal Not Detected" screen to appear but only for a split second before the monitor turned back off. From previous readings regarding capacitors I knew immediately that this was most likely the issue and that I should start by looking at the Power board.

    Strangely, I am unable to locate any information regarding this specific power board save one site that's in Russian where they replaced 6 capacitors on the board. (By the way, the power board includes the inverter all-in-one. Model: S9 Serise POWER B / D REV: A10 11S92-008A. And yes, "Serise" is misspelled on the actual board as well ) The 6 they referred to did not look good on my board (bulging a bit on top, and very dark in color (I compared one of them with the exact same cap in a different part of the board), which I suspect is from the heat. I decided to replace the 6 caps and here's the line-up:

    Original Capacitors
    G-Luxon LU Series Capacitors
    • 2 x G-Luxon LU 470uF 16v, Ripple: 1000 (8mmx15mm)
    • 2 x G-Luxon LU 1000uF 16v, Ripple: 1820 (10mmx20mm)
    • 2 x G-Luxon LU 1000uF 10v, Ripple: 1430 (10mmx16mm)


    I have ordered the following to replace them:
    Panasconic FM Series Capacitors
    • 2 x Panasonic FM 470uF 16v, Ripple: 1240 (8mmx15mm) EEUFM1C471L
    • 2 x Panasonic FM 1000uF 16v, Ripple: 2180 (10mmx20mm) EEUFM1C102
    • 2 x Panasonic FM 1000uF 10v, Ripple: 1790 (10mmx16mm) EEUFM1A102


    Did I make the right decision on these? Just looking for some backup to help me sleep at night. I won't be able to let you know if this repair worked for a while since DigiKey is backordered on one of the items. Thanks everyone!
    Tags: None
    #2
    Re: CTX S762G - Some Questions...

    Also, I had at first (being the novice at this that I am) tried to replace the caps with cheapo Xicon ones. When I plugged the LCD in, not even the green power LED on the front came on anymore. I realized after I had done this that the ripple on the ones I bought were no where near close to the originals. Would this be the reason that the monitor did not come on? Can the ripple really make it so that the monitor wouldn't even power on or do I have something else going on here now?

    Comment

      #3
      Re: CTX S762G - Some Questions...

      Well, I would have gone with caps with lower ripple, rather than (slightly) higher.

      I used Xicon caps when I was young(er) and didn't know any better without any problems. Of course, they don't give me the 'warm fuzzy feeling' that Panasonics would have. Carefully look over the soldering you did, and make sure they are installed properly. You wouldn't be the first guy to install a replacement backwards.

      As always, pictures are a big help.

      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

        #4
        Re: CTX S762G - Some Questions...

        About the pictures, I would have included some but I am regretfully at work at the moment. The board actually has negative indicators under the caps and on top of that I wrote down which way they face. I thought perhaps the lower than half ripple of the Xicons could have been causing the monitor to not power up. I thought I may have read some post from a while back regarding if the CCFL Drive Controller doesn't receive exactly what it's looking for it won't power on. I will tell you this though, before I installed the Xicons, there was a ticking coming from the transformer which I assumed meant a short somewhere. After replacing the caps, the tick was no longer there...but once again...no power LED. I can hear the transformer though. I'm starting to think I may have done something while replacing the caps to cause this...but I'm not sure. Should the monitor have come back on with the Xicons even though they had very low ripple?
        Last edited by pantherts; 03-17-2009, 12:31 PM.

        Comment

          #5
          Re: CTX S762G - Some Questions...

          Okay! Pictures are uploaded (thanks to my wonderful girlfriend at home who took some pictures for me and plugged the camera into the home computer for me to remote grab 'em). I have uploaded them on my personal site because of their size (avg. of about 2mb a piece). Quite large, detailed images. Notice I have the caps removed, and you can clearly see the PCB suffered some heat damage which I'm sure lead to the original caps failing. Here are the pictures:

          Side View
          Angled View
          Top View 1
          Top View 2
          Top View 3
          Top View 4
          Bottom View 1
          Bottom View 2

          Sorry for the extreme size of these images but I wanted to make sure everything was "zoomable".

          Comment

            #6
            Re: CTX S762G - Some Questions...

            Definitely signs of excessive heat in the area where the caps were. That is definitely an item of concern. I also see a couple of other thing to wonder about.

            In both pictures of the bottom of the board, the solder joints for RT1 don't look too good. I'm not sure if that is an artifact of the picture, or if it's real.

            Again, on the bottom, I'm interested in the part number of U1.

            And lastly, on the top, C25 may be of interest.

            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: CTX S762G - Some Questions...

              I will check out RT1 closer when I get home, but I think you're seeing some artifacts of the picture. Part U1 is the PWM controller SG6841S (Datasheet). C25 is the small cap near the transformer...is that the part you're referring to?

              Also, here is a better shot of the RT1 area along with the PWM controller U1:

              Bottom View 3

              If you zoom in on the lower right corner of the picture, you'll see a red rectangle around RT1. I think those are okay but I can check like I said when I get home.
              Last edited by pantherts; 03-17-2009, 03:18 PM.

              Comment

                #8
                Re: CTX S762G - Some Questions...

                I'd agree, the solder joints on RT1 look good. I'd replace C25 if it's the same brand as the ones that failed. If it's bad the regulator will attempt to start, but will fail to sustain operation.

                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

                  #9
                  Re: CTX S762G - Some Questions...

                  Okay, I will look into replacing C25. I still find it strange that before I replaced the 6 problematic caps the monitor was blinking the front LED and would sometimes come on for a split second. I replaced them and then got nothing. The only difference with the new caps I'm getting is that they are the correct voltage and have higher ripple ratings. If I put the Xicons back in, can I do voltage testing? Or should I just wait for the new caps?
                  Last edited by pantherts; 03-17-2009, 05:12 PM.

                  Comment

                    #10
                    Re: CTX S762G - Some Questions...

                    I'd wait for the new caps. Every time you take a soldering iron to the board you increase the chance of damaging something....

                    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

                      #11
                      Re: CTX S762G - Some Questions...

                      Okay, well then in the meantime since I have lots of time to wait for these things (Estimated ship date from DigiKey is the 30th) is there some multimeter tests I can do? I already checked continuity on all the SMD fuses marked "0" on the bottom of the board and all checked out okay. I'd like to check the transistors or voltage regulator but I know that with them being in circuit I could get wacky results. Anything else I could check to make sure I'm not going to require some more parts?

                      Comment

                        #12
                        Re: CTX S762G - Some Questions...

                        Originally posted by pantherts
                        Okay, well then in the meantime since I have lots of time to wait for these things (Estimated ship date from DigiKey is the 30th) is there some multimeter tests I can do? I already checked continuity on all the SMD fuses marked "0" on the bottom of the board and all checked out okay. I'd like to check the transistors or voltage regulator but I know that with them being in circuit I could get wacky results. Anything else I could check to make sure I'm not going to require some more parts?
                        I'd check F1, the red cylindrical object next to the power input connector and D2, the bridge rectifier.

                        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

                          #13
                          Re: CTX S762G - Some Questions...

                          Okay, F1 the red cylinder which I'm guessing is a fuse checks out for continuity (I'm thinking this is a fuse because it is connecting the "hot" lead of the plug to the rest of the circuitry. I can barely read "5A250V" on it but there might be more before the "5" though it is hidden by the white stuff).

                          I tested the bridge rectifier at D2 and it checked out fine.

                          Comment

                            #14
                            Re: CTX S762G - Some Questions...

                            Okay, finally after a month of waiting for backordered parts I have the new caps in place. I plugged her in. I'm getting further! The LCD blinks rapidly on and off. I can hear a popping in the built in speakers. Does this mean that there could be more caps bad on this power board? Or could this be a different problem now?

                            I'm open for suggestions of what to test and what could be the issue here. Thank you everyone!

                            Comment

                              #15
                              Re: CTX S762G - Some Questions...

                              Okay, I think I messed up. While I was testing voltages, my unsteady hand slipped and crossed some pins on a part. I've looked for the part online but I cannot identify it. Here's a description of it:

                              It stands vertical off the board and has three pins going into the board. It has a screw going through the top of it into a thick aluminum heat sick. The lettering on it appears exactly as follows:

                              K
                              C2804
                              Y 334

                              I'm pretty sure it may be a voltage regulator if that helps at all. Can someone tell me what this part is (datasheet?) and what I could have done to this poor board now? Thanks everyone.

                              Comment

                                #16
                                Re: CTX S762G - Some Questions...

                                http://www.alldatasheet.com/view.jsp...=C2804&q=C2804

                                maybe this one..?
                                http://www.alldatasheet.com/datashee...C/KTC2804.html

                                Comment

                                  #17
                                  Re: CTX S762G - Some Questions...

                                  THe KTC2804 looks like the part I described. Right now, if plugged in I'm reading just over 12v DC coming out of the center pin. Both side pins are reading in the 4-4.5v range. This tells me that it's definitely fried because I believe that it should be opening and closing depending on the power status. As a follow up, before I fried this module, the LCD was flashing on and off quickly and there was no power status LED on the front. I've replaced all capacitors except the largest one that I hear rarely goes bad.

                                  I'd like to put another order in for parts but I'd like to make sure that I'm ordering everything that I need. Without that voltage regulator, can I do any more testing?

                                  Comment

                                    #18
                                    Re: CTX S762G - Some Questions...

                                    Just real quick, here is the part that I fried while testing voltages. I'm pretty sure I touched the pin on the right side of it to the heatsink behind it and that is what caused it to spark. After that the LCD stopped flashing but I could still hear a small ticking coming from the transformer.

                                    Part Highlighted In Red

                                    Comment

                                      #19
                                      Re: CTX S762G - Some Questions...

                                      I'm sorry for so many posts here in a row but I have gotten the backlight to come on despite the voltage regulator being most likely toast. I haven't left it plugged in for more than a few seconds but the backlight stays on despite if I press the power button on or off. The green LED for the power light does go off though when the button is pressed. Nothing is being displayed on the screen though, no menu or message stating no video signal detected. Can someone please confirm that the reason there is no image and the backlight doesn't "know" when to turn off is because of the faulty volt regulator?

                                      In the pic labeled Bottom View 1 on post #5, the volt regulator is the three pin labeled Q3 near the bottom of the pic. In post #18 I have highlighted the device in a red bounding box. Thanks everyone! And once again sorry for this running diagnosis. (I'm pretty sure I'm getting somewhere though since I'm no longer getting a clicking out of the transformer and the backlight is now coming on)

                                      Comment

                                        #20
                                        Re: CTX S762G - Some Questions...

                                        Q3 indicates it's a transistor, not a regulator. The best test is to unsolder it and measure the resistance. between the legs.

                                        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

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