Announcement

Collapse
No announcement yet.

Samsung 940BW won't turn on

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
    #1

    Samsung 940BW won't turn on

    A number of months back my Samsung 19" widescreen stopped working after a lightning strike. I haven't had the time to mess with it until now, but I'd really like to get it working again. I'm no expert at component level repair (nor surface mount soldering) and at this point I'd be happy just to narrow the problem down to the controller or the power board. Components on the power board are large enough that I could probably replace them myself, but if the controller is fried, then I'll just have to replace it.

    Neither board has any visibly-damaged components, but they never do, do they? The fuse on the power board still has continuity but I can't find one on the controller... maybe I'm not looking hard enough. At least some of the caps on the power board are charging. I'm not reading a voltage between the ground and any other pins on the harness that goes between the 2 boards.

    The front control panel connects into the logic board. Is there a way to fool the power board into powering up the inverters and backlights? Pins on the harness between the boards are labeled B-Dim, +13V, GND, +5.1V, A-Dim, and O/F. Any ideas would be greatly appreciated

    Decent-sized photos attached, but if you want the REALLY big ones, they're linked below... I figured 4MB each was too big to embed.

    http://delturcious.net/samsung/IMG_1044.JPG
    http://delturcious.net/samsung/IMG_1047.JPG
    Attached Files
    Tags: None
    #2
    Re: Samsung 940BW won't turn on

    are you getting any voltage (DC) on the main filter cap?
    that's the huge one.
    be careful though, as it holds (or should hold) roughly 1.4 times the line voltage (around 170V DC for 120V and around 320V for 230V countries)

    if not, the bridge rectifier (flat black box next to the huge main filter cap) might have failed.
    the MOV (green disc in the bottom left of the PSU pic) looks like it's intact. they usually explode pretty violently or burn up if something goes wrong with them.

    Comment

      #3
      Re: Samsung 940BW won't turn on

      Originally posted by Scenic View Post
      are you getting any voltage (DC) on the main filter cap?
      that's the huge one.
      Yup, getting ~165-170V according to my $3 multimeter and the MOV is intact
      Last edited by delturcious; 04-03-2011, 06:53 PM. Reason: forgot to answer one of the questions

      Comment

        #4
        Re: Samsung 940BW won't turn on

        You can plug the Power Supply into the mains,plug in the backlights,and apply approx 3volts minimum(from a battery perhaps),between theO/F pin (positive) and GRound(neg).If all is well then the Lights should come on.

        Comment

          #5
          Re: Samsung 940BW won't turn on

          Originally posted by delturcious View Post
          I'm not reading a voltage between the ground and any other pins on the harness that goes between the 2 boards.
          If you are not getting secondary voltage as per above, the SMPS hasn't started. It could be the small cap around the SMPS is bad or the SMPS controller is bad.

          1) What is the DC voltage across the small electrolytic capacitor just above JP104? Is it stable or fluctuating?

          2) What brand and series is this cap?

          3) What is the uF and voltage rating on the cap?

          I figured 4MB each was too big to embed.
          I'm especially grateful.
          --- begin sig file ---

          If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

          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

            #6
            Re: Samsung 940BW won't turn on

            Well I don't know if this will help or not but my Samsung SyncMaster 940BW died during storm as well. My solution was pretty simple though as C30 and C205 were obviously blown. They were C30(25V 470uf, CapXon) and C205(16V 1000uf, SAMWHA). Simply replacing these 2 capacitors was all it took for me.
            Attached Files

            Comment

              #7
              Re: Samsung 940BW won't turn on

              Originally posted by stray77 View Post
              They were C30(25V 470uf, CapXon) and C205(16V 1000uf, SAMWHA).
              Capxon has a poor reputation with forum members here. The standard recommendation is to replace all the electrolytic capacitors, except the largest one which rarely fails, with quality low ESR ones like

              https://www.badcaps.net/forum/showthread.php?t=2280
              --- begin sig file ---

              If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

              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

                #8
                Re: Samsung 940BW won't turn on

                hello everyone, just want to ask if there is a schematic diagram of this samsung 940bw? (because i, too, also own one). I would like to learn it somehow....

                My lcd 940bw problem is that when my pc is turned on, the monitor wont start... it takes too long for it to show visuals (before it ony takes 5-30 minutes, but seems like getting worse coz it took hours 5-12 hours before before it shows visuals...

                Ive been told that inverter is the problem and some caps... but i dont know exactly where it shows...

                highly appreciate for all your assistance....

                (my first post here in BadCAPS.net :-))

                Comment

                  #9
                  Re: Samsung 940BW won't turn on

                  Originally posted by tombshot View Post
                  Ive been told that inverter is the problem and some caps... but i dont know exactly where it shows...
                  Your symptoms sounds like bad caps. As the lcd gets warm, the ESR (ohms) of the caps decrease. When the lcd is off for a while, the cap's ESR is high and doesn't allow the lcd to turn on.

                  Take it apart and see the picture in post #6 showing bad caps. We do, however, want to see pictures of YOUR lcd.

                  PS. 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
                  --- begin sig file ---

                  If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                  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

                  Previous template Next
                  Working...
                  X