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Beko 30WLB500S - Sound, no picture

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    Beko 30WLB500S - Sound, no picture

    I have this LCD TV, and it's giving sound but no picture. Some seconds (maybe 15-20secs) after starting up I can see a quick flash of a picture, but it disappears, sound remains.

    A quick google finds this:
    NR 30WLB500S-(CHASSIS-L4B)-No pictures sound ok back light can see for 1,2 second -problem in inverter board (V144-301) faulty one of hight voltage transformers (4006A4250037).
    I took the inverter board out (attached), and can see it has "Darfon V144" markings on it.

    Is there any good way of testing the voltage transformers? Is it likely to be 1 or all of them faulty? Any other checks I should be making?

    Thanks.
    Attached Files

    #2
    Re: Beko 30WLB500S - Sound, no picture

    You have found good advice. These inverters and transformers are notorious for shorted secondaries. (Darfon is the Yugo of the LCD world.) It is likely to be only one transformer. If you look at the picture, the pins are numbered. Pins 1 & 8 are the ends on one secondary winding; pins 4 & 5 are the end of the other secondary winding.

    Testing is easy if you have an DMM. Set it on the 2K ohms range and measure each transformer from 1-8 and from 4-5, making a note of each reading. The windings typically measure about 1000 ohms, but this can vary from lot to lot. In a single batch I would expect them to match to within 3%. What you are looking for is a secondary that is significantly different (lower) resistance than the rest, or that reads open.

    Once you have found it, Chip-quik makes it easy to remove the transformer. Replacements are available on eBay, or a company called Electronica USA carries them.

    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: Beko 30WLB500S - Sound, no picture

      Thanks for the pointers Bill, this is what I get when I measure the 1-8's and 4-5's:

      1-8: 4-5:
      943 944
      932 933
      921 926
      930 928
      927 931
      932 931
      942 944
      942 941

      What do you think, the only one that stands out to me is #3, but it still looks alright, I think.

      EDIT: I had a closer look at the power board, and there are a couple of bulging caps, I'll put it back together a bit, and see what voltages are coming off it's connectors.
      Last edited by tmcw; 06-11-2011, 07:49 AM.

      Comment


        #4
        Re: Beko 30WLB500S - Sound, no picture

        Ok, I checked the voltage on the 2 connections coming off the powerboard. Both are supposed to have +24V, I was getting about 15V on CN3, and 0V on CN2. You can probably see the 2 caps nearest the bottom-left corner with the bulging, and they were squealing too.

        CN3 is connected to the videoboard, and CN2 is connected to a small board towards the top-right of the main picture of the back of the TV, where it is split into 2 and goes to the 2 connections on the inverter. There are 4 wires from one of the connections on the inverter looped back to the videoboard.

        So, definitely a problem at CN3 with the bulging caps and 15V, but what about CN2 with 0V? Is it possible that that part of the circuit doesn't get switch-on until other parts check-out? That power control pin is jumpered over to that side where I was seeing 0V. Any other considerations?
        Attached Files
        Last edited by tmcw; 06-11-2011, 08:34 AM.

        Comment


          #5
          Re: Beko 30WLB500S - Sound, no picture

          As far as the caps go, it looks like capxon caps. The worse caps ever. After you change all eight of the tall dark caps, you should be OK. This will affect your output voltages to the inverter board.
          The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

          Comment


            #6
            Re: Beko 30WLB500S - Sound, no picture

            Capxon does not have a good reputation on this forum. Since 2 were obiviously bad, the rest could be considered bad by reason "guilty by association".

            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.

            Most members here will recommend that you replace ALL capacitors with reputable brands from reputable sellers. Brands like Rubycon, Panasonic, and United Chemicon are suggested. A list of recommended caps can be found at

            https://www.badcaps.net/forum/showthread.php?t=2280
            Last edited by retiredcaps; 06-11-2011, 12:53 PM.
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            Comment


              #7
              Re: Beko 30WLB500S - Sound, no picture

              Thanks, yes, they are CapXon caps, all 8 are 1000uF, 4x25V on the left, 4x35V on the right.

              I actually got 3 of these TVs today, a caretaker at work held onto them for me. Was thinking maybe do a Frankenstein, and get at least one working, but a caps change is no big deal. One has a smashed screen, one seems to have a bit of water in the screen, but the 3rd seems to be fine. If the wet one doesn't dry out, I should be good for various boards for a few years on the one with the good screen.

              What's the convention on upgrading these caps, what would be a good manufacturer/series? Also, keep at 1000uF obviously, and up the 25V to 35V, and the 35V to 50V, or just up them all to 50V?

              EDIT: Forgot to say that the other 2 TVs, there were 6 caps bulging in one, and 7 in the other, a few also discharged a little bit on the top, but all confined to these 2 sets of caps.
              Last edited by tmcw; 06-11-2011, 12:47 PM.

              Comment


                #8
                Re: Beko 30WLB500S - Sound, no picture

                Originally posted by retiredcaps View Post
                Capxon does not have a good reputation on this forum. Since 2 were obiviously bad, the rest could be considered bad by reason "guilt by association".

                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.

                Most members here will recommend that you replace ALL capacitors with reputable brands from reputable sellers. Brands like Rubycon, Panasonic, and United Chemicon are suggested. A list of recommended caps can be found at

                https://www.badcaps.net/forum/showthread.php?t=2280
                Thanks, yes, I'll get enough to do all 3 powerboards. And you were right about the "guilty by association", I could see that when I looked at the other 2 powerboards. I used Rubycons the last time I rebuilt a powerboard, so I'll have a look at the thread and see what's recommended from them.

                Thanks for all the help.

                Comment


                  #9
                  Re: Beko 30WLB500S - Sound, no picture

                  Ok, replaced the 8 caps on one of the power boards with Panasonic FC's, but I'm still seeing about 15V on one connector (CN3), and 0V on the other one (CN2).

                  Although I used the same capacitance and voltage (1000/25 and 1000/35), the caps are not the same height/width; would this make much of a difference?

                  Comment


                    #10
                    Re: Beko 30WLB500S - Sound, no picture

                    Originally posted by tmcw View Post
                    Although I used the same capacitance and voltage (1000/25 and 1000/35), the caps are not the same height/width; would this make much of a difference?
                    Height and diameter will make no difference in this context.

                    Did you replace the 4 smaller caps in the middle of the power board?

                    One of the smaller caps is the startup cap for the SMPS and they can go bad without bloating.
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                    We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                    Please do not post inline and offsite as they slow down the loading of pages.

                    --- end sig file ---

                    Comment


                      #11
                      Re: Beko 30WLB500S - Sound, no picture

                      I have now, but the caps I used were Jackcon caps, I don't have any better to hand. Am I better waiting until I get good branded caps to replace them, or would you expect them to work initially at least?

                      I'm also getting a bit of a buzz in the area of the big cap or the yellow transformer beside it. That could be normal though.

                      Also, I was testing a few of the pink resistors, and a few of them are testing open, the ones that are mounted parellel to the board. Is that to be expected?

                      Comment


                        #12
                        Re: Beko 30WLB500S - Sound, no picture

                        Scanning through your last couple of posts, after you changed the caps out, did you put the set back together and test it? or did you just check for output voltages?
                        The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

                        Comment


                          #13
                          Re: Beko 30WLB500S - Sound, no picture

                          I've put it back together.

                          When I switch the TV on, it's like it's in standby, the red light near the power switch is on. When I press the PR+ button, I can hear the buzz/crackle on the powerboard as it gets power, then a few seconds later (between 5 and 10 secs) I get a flash of static and can see a channel name in one corner, but the screen stays blank after that.

                          Comment


                            #14
                            Re: Beko 30WLB500S - Sound, no picture

                            Have attached a photo of the solder side of the power board, quite a bit of heat damage around the transistors in the middle of the board.

                            I connected the set up to a SCART input, and when the screen momentarily switched on, I could see the correct picture, and noticed that the sound continued after the picture switched off again.

                            Any pointers on what to test next?
                            Attached Files

                            Comment


                              #15
                              Re: Beko 30WLB500S - Sound, no picture

                              Originally posted by tmcw View Post
                              Have attached a photo of the solder side of the power board, quite a bit of heat damage around the transistors in the middle of the board.

                              I connected the set up to a SCART input, and when the screen momentarily switched on, I could see the correct picture, and noticed that the sound continued after the picture switched off again.

                              Any pointers on what to test next?
                              Classic description of 'Two Seconds to black'. Usually caused by bad caps in the power supply or inverter, a problem with a CCFL or the wiring to them, or a bad inverter transformer.

                              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: Beko 30WLB500S - Sound, no picture

                                You're dead right Bill. I tested the inverter transformers and found one of them having 4.7k ohms on one of the 1-8 pins, when all the rest of them are about 970 ohms. This is a different inverter to the one I tested the first day.

                                As I said before, I have 3 of these models of TV, but the inverters between 2 of them that I've opened are different. Should they be interconvertable? I'm not so sure, as I noticed on the one that I'm testing right now (with bad inverter transformer) there is a hand-soldered jumper on the AV board that's missing on the other 2 models.

                                I might just test the recapped powerboard in the set that I tested the first day (it had tested good inverter transformers).

                                Comment


                                  #17
                                  Re: Beko 30WLB500S - Sound, no picture

                                  Ok, I put the recapped power board into the set that has good inverter transformers, and it's giving 2S2B, although it seems the screen is lit a bit longer than before.

                                  With the set "on", I also tested the power on the 2 connectors off the power board:

                                  CN3 (going to AV board) is still outputting 15V (marked 24V)
                                  CN2 (going to inverter board) is now outputting 24.5V (marked 24V)

                                  So it seems that the wiring has some feedback loop to the power board to tell it to switch on the inverter side of the power board. And the inverter should be getting the correct voltage.

                                  Now, I've replaced the caps on the power board, EXCEPT the big 150uF/450V cap (also a Capxon). If it was bad, would I be getting the good 24V on CN2? Could it still be contributing to the the bad 15V on CN3, and could this bad 15V on CN3 going to the AV board still be causing the 2S2B?

                                  Comment


                                    #18
                                    Re: Beko 30WLB500S - Sound, no picture

                                    Another question regarding the CCFL and wiring to them - how can I test these, is it a simple continuity test for the wiring? How about the CCFL, how do I test that?

                                    Also, although the voltage on the power board for connection CN3 is about 15V and the board has a label on it saying "24V", would the 15V be enough to run the videoboard that this 15V is going to?

                                    Comment


                                      #19
                                      Re: Beko 30WLB500S - Sound, no picture

                                      CCFLs are best tested by substitution or direct observation. As for the wires, physical examination works best.

                                      As an example, a friend gave me a 19" Dell monitor with the two seconds to black problem. By hooking up a test CCFL to each connector in turn I was able to establish the monitor continued to work only when the good CCFL was connected to connector #3. I also noticed the typical pinkish tint in the display if the original CCFL was hooked up to any connector.

                                      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


                                        #20
                                        Re: Beko 30WLB500S - Sound, no picture

                                        Ok, I was looking at the power board again, and noticed the sticker on the large cap. I originally thought the sticker related to the cap, but it seems it relates to the board as it has 2 outputs on it, 15V and 24V, so it seems that the power board is good after all. The board has 24V and 24V printed on it, but it seems that was probably for a different revision of board.

                                        So, I've tested the transformers on the inverter board, and they seem to be ok (on one of the boards at least). Is it possible to safely check the voltages on the inverter output to the panel (blue and pink leads), just to be sure that the inverter is ok?
                                        Attached Files
                                        Last edited by tmcw; 06-21-2011, 03:24 AM.

                                        Comment

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