Dell E173FPf with Su'scon caps

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  • yotefn
    Member
    • Mar 2012
    • 11
    • USA
    #1

    Dell E173FPf with Su'scon caps

    Hi, monitor has no power at all, no LED at power button.
    Attached are pictures of the board, the video and power are on the same board.
    Probing with a meter, I get 169VDC at the big filter cap, and at the primary connections at T850. I do not measure any other voltages anywhere else on the board, including any direction on the secondary of the transformer. My guess at this point would be the transformer is shot. It's marked "SPW-039 TDK X 0434". I have no idea what the output power or current would be.

    2 Questions:
    1)Does anyone have any ideas what might be wrong or what else I should measure?
    2)Without a datasheet posted online for the transformer, anyone know how to replace it?

    Thanks
    Attached Files
    Tags: None
    • selldoor
      Slow Learner
      • Dec 2010
      • 7870
      #2
      Re: Dell E173FPf with Su'scon caps

      Check the resistances of the secondary windings on the transformer
      Last edited by selldoor; 04-27-2012, 12:05 PM.
      Please upload pictures using attachment function when ask for help on the repair
      http://www.badcaps.net/forum/showthread.php?t=39740

        Comment

        • jetadm123
          Badcaps Legend
          • Feb 2010
          • 2169
          #3
          Re: Dell E173FPf with Su'scon caps

          Try reading the DC voltage of the vcc pin of U850. Sorry , I can't read the part # of U850, so you'll have to look up the spec sheet yourself.

            Comment

            • selldoor
              Slow Learner
              • Dec 2010
              • 7870
              #4
              Re: Dell E173FPf with Su'scon caps

              I have been reading other posts
              https://www.badcaps.net/forum/showthread.php?t=9297

              https://www.badcaps.net/forum/showth...hlight=E173FPf


              They have both had problems around R852 q850 and one person came in and said they fixed one by replacing these ,so perhaps you should check yours.
              Spec sheet may be in one of these threads
              Please upload pictures using attachment function when ask for help on the repair
              http://www.badcaps.net/forum/showthread.php?t=39740

                Comment

                • retiredcaps
                  Badcaps Legend
                  • Apr 2010
                  • 9271
                  #5
                  Re: Dell E173FPf with Su'scon caps

                  Originally posted by jetadm123
                  Try reading the DC voltage of the vcc pin of U850.
                  And the DC voltage across C857. Note if voltages are stable or fluctuating.
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                    Comment

                    • yotefn
                      Member
                      • Mar 2012
                      • 11
                      • USA
                      #6
                      Re: Dell E173FPf with Su'scon caps

                      Woa! After seeing this page and billy66's post:

                      https://www.badcaps.net/forum/showth...ht=u850&page=2

                      Monitor wont power on. No LED, no picture, nothing. The transformer T850 clicks once or twice (sounds like it is charging up). Voltages are as follows:

                      - Filter cap: 156V
                      - U850 Pin 1- 0
                      2- 2.6V
                      3- 24.8v
                      4- 1.29v
                      5- 4.5v
                      6- 0.75v
                      7- 24.7v
                      8- 0.25v
                      I measured my U850, which I assume is the PWM chip. Other than pin 1, I think every pin measured -68.7VDC (negative), except for one pin which measured positive same voltage.

                      The center pin on Q850 was also -68.7VDC

                      Now I'm no electronics geek, but after rectification why would I be measuring negative voltage? If the whole thing is shorted out I think I'll just call it a day, the monitor only sells for $50 on ebay.
                      Last edited by yotefn; 04-28-2012, 09:35 PM.

                        Comment

                        • retiredcaps
                          Badcaps Legend
                          • Apr 2010
                          • 9271
                          #7
                          Re: Dell E173FPf with Su'scon caps

                          Originally posted by yotefn
                          Other than pin 1, I think every pin measured -68.7VDC (negative), except for one pin which measured positive same voltage.

                          The center pin on Q850 was also -68.7VDC

                          Now I'm no electronics geek, but after rectification why would I be measuring negative voltage?.
                          Negative voltage is a result of you using the wrong ground for your black probe. There is a hot ground and cold ground. Usually the cold ground are the ground screws and chassis. I normally use the negative leg of the large filter capacitor for hot ground.
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                            Comment

                            • yotefn
                              Member
                              • Mar 2012
                              • 11
                              • USA
                              #8
                              Re: Dell E173FPf with Su'scon caps

                              OK, that's good to know.

                              Here's a list of measurements:

                              Across primary and secondary windings of transformer is non-infinate resistance so I guess thats good for now considering all the other bad measurements.

                              Using filter cap as ground:

                              to cold ground: 67VDC

                              I850 Pins 1 and 2, U801, U802 U851: 67VDC (all pins of these same as cold ground)

                              I850 Pins 3,4: 0V

                              U850
                              Pin 1,2,4,6: 0VDC
                              Pin 3: 4.4
                              Pin 5: 0.1 (consistently bumped meter slightly)
                              Pin 7,8: 1.7

                              Center of Q850: 170VDC

                              Across c857: 1.7VDC

                              U850 part number SG6841S

                              http://pdf1.alldatasheet.com/datashe...C/SG6841S.html

                              Any ideas?
                              Last edited by yotefn; 04-29-2012, 08:20 AM.

                                Comment

                                • retiredcaps
                                  Badcaps Legend
                                  • Apr 2010
                                  • 9271
                                  #9
                                  Re: Dell E173FPf with Su'scon caps

                                  Originally posted by yotefn
                                  U850
                                  Pin 1,2,4,6: 0VDC
                                  Pin 3: 4.4
                                  Pin 5: 0.1 (consistently bumped meter slightly)
                                  Pin 7,8: 1.7

                                  Across c857: 1.7VDC
                                  In order for the SMPS IC to start, it requires 16V DC (pin 7).

                                  Either C857 is bad or the SMPC IC is bad. Start by replacing C857 with something like a Panasonic FC series cap and retest.
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                                    Comment

                                    • yotefn
                                      Member
                                      • Mar 2012
                                      • 11
                                      • USA
                                      #10
                                      Re: Dell E173FPf with Su'scon caps

                                      Recapped C857, no change.

                                      Analyzing the datasheet and looking at the voltages on U850 at pins 7 and 8, I checked continuity with the IC on the board of those two pins and they were shorted. So I removed the IC and checked again and they're shorted. Ordered a new IC on ebay from Hong Kong (no one reputable carries the chip anymore), will replace and report.

                                      Thanks for your help.

                                        Comment

                                        • retiredcaps
                                          Badcaps Legend
                                          • Apr 2010
                                          • 9271
                                          #11
                                          Re: Dell E173FPf with Su'scon caps

                                          Originally posted by yotefn
                                          Analyzing the datasheet and looking at the voltages on U850 at pins 7 and 8, I checked continuity with the IC on the board of those two pins and they were shorted.
                                          Good job finding the short. Yes, if you can't find it at digikey or mouser, ebay is a good alternative.
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                                            • yotefn
                                              Member
                                              • Mar 2012
                                              • 11
                                              • USA
                                              #12
                                              Re: Dell E173FPf with Su'scon caps

                                              Alright, replaced U850, but now I have fluctuating voltage across C857 (equal to pins 1 and 7 on the SMPS) between 12.1V and 15.8V, with no power to other pins at all, other than pin 3 at 18V but fluctuating slightly. Replaced cap C857 again with no change.

                                                Comment

                                                • retiredcaps
                                                  Badcaps Legend
                                                  • Apr 2010
                                                  • 9271
                                                  #13
                                                  Re: Dell E173FPf with Su'scon caps

                                                  Follow along with this thread. There are a number of suggestions that you can try.

                                                  https://www.badcaps.net/forum/showthread.php?t=20469
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                                                  Please do not post inline and offsite as they slow down the loading of pages.

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