No backlights

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  • Mike Jenk
    Senior Member
    • Jul 2012
    • 113
    • USA

    #1

    No backlights

    So I have this Westing house LTV-27w2 and has the 2 seconds to black, can see image with light and has audio. I just wanted some input on the inverter board pin out CN2 , if some one has it to ensure my voltages are correct when turned on. If some one remembers where the post is for using another bulb in the place of mine could you let me know, I don't have any spares.

    Thanks.
    Attached Files
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: No backlights

    You have a Darfon board, any time you have 2 secs to black with a Darfon it is essential to check the transformers. See pic.

    All transformers should measure with ±3% of each other. There may be a bad one on the board which measures otherwise.

    edit: Check both sides of the transformer too, not just the side I highlighted in the image.
    Attached Files
    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

    Comment

    • Mike Jenk
      Senior Member
      • Jul 2012
      • 113
      • USA

      #3
      Re: No backlights

      Originally posted by tom66
      You have a Darfon board, any time you have 2 secs to black with a Darfon it is essential to check the transformers. See pic.

      All transformers should measure with ±3% of each other. There may be a bad one on the board which measures otherwise.

      edit: Check both sides of the transformer too, not just the side I highlighted in the image.
      Thanks, I thought it might come to that, did a little research and these things are about 20.00 a pop. re-man board was about fifty and hate to have more problems later will let you known later, taking them out now.

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: No backlights

        Absolutely no need to remove them for the test, you can do it in circuit.

        Likely, only one will have failed.
        Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
        For service manual, schematic, boardview (board view), datasheet, cad - use our search.

        Comment

        • Mike Jenk
          Senior Member
          • Jul 2012
          • 113
          • USA

          #5
          Re: No backlights

          Originally posted by tom66
          You have a Darfon board, any time you have 2 secs to black with a Darfon it is essential to check the transformers. See pic.

          All transformers should measure with ±3% of each other. There may be a bad one on the board which measures otherwise.

          edit: Check both sides of the transformer too, not just the side I highlighted in the image.
          So I left one lead on terminal 1 then went around to each pin 2-8 and then repeated on all of them exactly the same way since the board is labeled with pin numbers. The transformer numbered as 1 in red measured between 1 and 4 had more then the 3% as compared to the other 6 transformer. I do not get 20K as you labeled. do they need to be removed to be more accurate. I really don't trust ohming things out in a circuit.
          Attached Files

          Comment

          • tom66
            EVs Rule
            • Apr 2011
            • 32560
            • UK

            #6
            Re: No backlights

            No, I meant you need to set your meter to 20k. They are typically 1-5k, can't remember exact figure right now. List all the readings you get on each transformer, and each side tested.
            Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
            For service manual, schematic, boardview (board view), datasheet, cad - use our search.

            Comment

            • Mike Jenk
              Senior Member
              • Jul 2012
              • 113
              • USA

              #7
              Re: No backlights

              Originally posted by tom66
              No, I meant you need to set your meter to 20k. They are typically 1-5k, can't remember exact figure right now. List all the readings you get on each transformer, and each side tested.
              Transformer 1
              Lead stays on pin1
              2= 2m
              3=2m
              4=10.3k
              5=11.1k
              6=1.96m
              7=1.99m
              8=2.7k
              Transformer 2
              Lead stays on pin1
              2=2m
              3=1.99m
              4=.3 ohms closed
              5=981
              6=1.99m
              7=1.99m
              8=977
              Transformer 3
              Lead stays on pin1
              2=1.86m
              3=1.86m
              4=19.99k
              5=20k
              6=1.9m
              7=1.99m
              8=960
              Transformer 4
              Lead stays on pin1
              2=1.91m
              3=1.91m
              4=.3
              5=957
              6=1.93m
              7=1.93
              8=950
              Transformer 5
              Lead stays on pin1
              2=1.99m
              3=2.01m
              4=19.98k
              5=20.93k
              6=2.02m
              7=2.02m
              8=953
              Transformer 6
              Lead stays on pin1
              2=2.17m
              3=2.17m
              4=.3
              5=969
              6=2.17
              7=2.17
              8=964
              Transformer 7
              Lead stays on pin1
              2=2.1m
              3=2.1m
              4=10.3k
              5=11.28k
              6=2.1m
              7=2.1m
              8=960

              I really appreciate helping me out, I have a ton of experience in Automotive, so I like to fix things.

              Comment

              • tom66
                EVs Rule
                • Apr 2011
                • 32560
                • UK

                #8
                Re: No backlights

                You need to measure across the two pins I've highlighted only, and the other two opposite. No other measurements are necessary for now.

                We see a lot of automotive techs here. I know how to change the oil and water in a car, but that's about where my knowledge ends...
                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                Comment

                • retiredcaps
                  Badcaps Legend
                  • Apr 2010
                  • 9271

                  #9
                  Re: No backlights

                  Originally posted by Mike Jenk
                  Transformer 1
                  Lead stays on pin1
                  8=2.7k
                  Transformer 1 pin 1 to 8 is bad. All the others in are the 950 ohms range.
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                  • retiredcaps
                    Badcaps Legend
                    • Apr 2010
                    • 9271

                    #10
                    Re: No backlights

                    I had a 4006 transformer die on me too and I got it from this seller

                    http://www.ebay.com/itm/150706796810
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                    • Mike Jenk
                      Senior Member
                      • Jul 2012
                      • 113
                      • USA

                      #11
                      Re: No backlights

                      Originally posted by retiredcaps
                      Transformer 1 pin 1 to 8 is bad. All the others in are the 950 ohms range.
                      Thanks guys I really appreciate it. Will you let you know how it turns out.

                      Comment

                      • retiredcaps
                        Badcaps Legend
                        • Apr 2010
                        • 9271

                        #12
                        Re: No backlights

                        Actually, I just stopped at transformer #1 and didn't look at the rest, but now that I do, #3, #5, #8 are bad in addition to #1.

                        Have a look at this diagram.

                        http://www.lcdparts.net/TransformerD...ProductID=2739

                        Remeasure all the transformers and report just S1-S2 and S3-S4.
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                        • retiredcaps
                          Badcaps Legend
                          • Apr 2010
                          • 9271

                          #13
                          Re: No backlights

                          Note some of the transformer pins might have a layer of "stuff". You may have to scrape off the "stuff" or get sharp probes to make good contact with the suspect transformers.
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                          • Mike Jenk
                            Senior Member
                            • Jul 2012
                            • 113
                            • USA

                            #14
                            Re: No backlights

                            Originally posted by retiredcaps
                            Note some of the transformer pins might have a layer of "stuff". You may have to scrape off the "stuff" or get sharp probes to make good contact with the suspect transformers.
                            Thats a good picture now I can see primary and secondaries. will report back in a few.

                            Comment

                            • Mike Jenk
                              Senior Member
                              • Jul 2012
                              • 113
                              • USA

                              #15
                              Re: No backlights

                              Originally posted by retiredcaps
                              Note some of the transformer pins might have a layer of "stuff". You may have to scrape off the "stuff" or get sharp probes to make good contact with the suspect transformers.
                              Heres the results

                              Transformer 1
                              1/8=2.7k
                              5/4=960
                              Transformer 2
                              1/8=975
                              5/4=980
                              Transformer 3
                              1/8=960
                              5/4=960
                              Transformer 4
                              1/8=960
                              5/4=950
                              Transformer 5
                              1/8=940
                              5/4=954
                              Transformer 6
                              1/8=958
                              5/4=964
                              Transformer 7
                              1/8=955
                              5/4=950

                              Comment

                              • retiredcaps
                                Badcaps Legend
                                • Apr 2010
                                • 9271

                                #16
                                Re: No backlights

                                Originally posted by Mike Jenk
                                Heres the results

                                Transformer 1
                                1/8=2.7k
                                5/4=960
                                Transformer 2
                                1/8=975
                                5/4=980
                                Transformer 3
                                1/8=960
                                5/4=960
                                Transformer 4
                                1/8=960
                                5/4=950
                                Transformer 5
                                1/8=940
                                5/4=954
                                Transformer 6
                                1/8=958
                                5/4=964
                                Transformer 7
                                1/8=955
                                5/4=950
                                Okay, 1 is bad for sure. Scraping that stuff made a big difference in the other readings as you can tell for youself.
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                                • Mike Jenk
                                  Senior Member
                                  • Jul 2012
                                  • 113
                                  • USA

                                  #17
                                  Re: No backlights

                                  Originally posted by retiredcaps
                                  Okay, 1 is bad for sure. Scraping that stuff made a big difference in the other readings as you can tell for youself.
                                  yes sir it did, can actually touch the legs, so I will get a new one and go from here. will measure it again when I remove it. sure is nice to have a diagram. Hate not knowing how something is wired. I really thank you guys for the help.

                                  Comment

                                  • Mr Bill
                                    Badcaps Veteran
                                    • Nov 2011
                                    • 648
                                    • USA

                                    #18
                                    Re: No backlights

                                    I've got a few 4006A transformers in my basement if you don't want to wait 14 days getting it directly from hong kong on ebay.

                                    Comment

                                    • Mike Jenk
                                      Senior Member
                                      • Jul 2012
                                      • 113
                                      • USA

                                      #19
                                      Re: No backlights

                                      Originally posted by Mr Bill
                                      I've got a few 4006A transformers in my basement if you don't want to wait 14 days getting it directly from hong kong on ebay.
                                      That would be awsome. you can PM me for details.

                                      Comment

                                      • retiredcaps
                                        Badcaps Legend
                                        • Apr 2010
                                        • 9271

                                        #20
                                        Re: No backlights

                                        Get a couple so you have a spare just in case. The ones at the "top" of the TV seem to fail more often than others. On mine, it was the 2nd from the top.
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