Monitor: Sony SDM-HS74P LCD

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  • forswitch38
    Member
    • Sep 2015
    • 10
    • USA

    #1

    Monitor: Sony SDM-HS74P LCD

    Before I explain the monitor, I want to say I'm new here. I also am a hardware noob. I've spent most of my life with computers. I've built one and I've programmed software. But I've never soldered on the circuit board or even hacked a graphics card to put a custom heatsink on it. See, at the hardware level, the most I've done is simply oiled some fans.

    Now onto the problem...

    This one came with a prebuilt computer in 2005. I think in 2010 or 2011 it started shutting off. I was able to keep it working by pressing menu buttons and changing the brightness--if I recall rightly. There was only a couple seconds when this would work, after which it would stay off. However, at some juncture, that stopped working. So probably in 2010 or 2011 I put this thing in storage and forgot about it. Now I picked it up again because I want to try and get it working again.

    Just to clarify, what happens is this:
    1) I turn it on
    2) Takes a few moments and then the screen lights up and shows whatever is on it. If the cord isn't connected, it'll say there's no signal. Otherwise, it'll act normally and show whatever is supposd to be onscreen.
    3) About 2 seconds later and it shuts off

    I've done hte flash light test and I know things are still showing on the screen. For example, I can see the bootup screen prompting me for my password. If it's in Widnows, I see whatever should be there. So I'm led to believe the inverter or CCFL's or wiring inbetween them is failing, meaning things ARE on screen, but not lit up.

    This--I believe--is the service manual:
    http://www.go-gddq.com/upload/2009_0...0810482821.pdf

    From what I can tell, it's a heavy construction, not lightweight. I removed the cover via screws, so I didn't have to monkey with any tabs, as I feared.

    Here's a picture of its layout:


    I lack the knowledge to make much sense of it. However, I'm guessing the power board is in the middle, the inverter board on the left and the processing board on the right.

    After I opened it up, I looked at the capacitors to see if any were bulging. Unfortunately, there was not any obvious bulging, as I had hoped there would be. There is a capacitor on the right which is crooked, but it doesn't look like there's any bulging underneath or above. (Ignore the fact it's discolored on the image above--that's my shadow) All of the capacitors looked, but except there were 2 which caught my interest. These:

    (Note the crack on the right one and the copper colored discoloration on the left)



    Disregard the green goo inbetween them. That was in other places. I'm led to believe it's to decrease vibration or maybe dissipate thermal heating. Is the copper colored spot on that one to be worried about? It looks almost like rust. The crack on the other one was immediately visible. It's not deep by any means. I also don't notice any seepage. While there's no bulging on either of them, these features felt worth asking about on these forums. Both of those appear to have a manufacturer which goes by "[ ] KY" It looks somewhat like OKY. They're 1000uf 25 volt 105C rated. There's a reference to "4(7) 9Y".

    Sadly (inconvenentily) I do not as yet have an ESR meter or capacitance meter. I do have a old meter of sorts, but I don't think it'd be of any use. It's named GB Instruments GMT-12A. Here's the manual:
    http://www.ps2netdrivers.net/manual/...mt-12a/#manual

    Neither do I have the other things I need: soldering iron, soldering wick or solder sucker, solder wire. So right now I'm just digging for information. I may also open it up again and take a look at the underside of the boards, as I've told they can show damage too. I also want to figure out how to get cleaner shots with the camara.

    Some questions I have:
    1) Are the capacitors available in the shop on this site rated as being low ESR?
    2) Do I HAVE to get low ESR capacitors? My local radio shack has some 1000uf 35 volt electrolytic capacitors, but it doesn't look like they're low ESR.
    3) If I buy these on badcaps.net, what should I get? And can I use paypal without debit/credit card?
    4) What tools do you recommend I buy to do this job, keeping in mind I'm VERY budget conscious. I might have a $50 budget for this, at most.

    EDIT: Mods feel free to remove one of my (duplicate) threads. ThIS one is a duplicate of my other thread, located at:
    https://www.badcaps.net/forum/showthread.php?t=49361

    I put it in that section first but then put it here because this seemed more apt.
    Last edited by forswitch38; 10-02-2015, 07:51 PM.
  • Agent24
    I see dead caps
    • Oct 2007
    • 4921
    • New Zealand

    #2
    Re: Monitor: Sony SDM-HS74P LCD

    If the capacitor is actually cracked then it would have dried out and could well be the cause of your problems.

    Being a switching PSU, yes, you need Low ESR. And no, Radio Shack don't have those.

    Re: the other thread for identification - can you post a photo showing the capacitor label rather than the top?
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

    Comment

    • budm
      Badcaps Legend
      • Feb 2010
      • 40746
      • USA

      #3
      Re: Monitor: Sony SDM-HS74P LCD

      You should also check those two blue caps next to the Inverter transforemrs and same for the two transistors (c5706/5706) next to the blue caps.
      This series are also known for having bad lamp assemblies.
      http://s807.photobucket.com/user/bud...?sort=3&page=1
      http://s807.photobucket.com/user/bud...?sort=3&page=1
      http://s807.photobucket.com/user/bud...?sort=3&page=1
      Last edited by budm; 10-02-2015, 08:57 PM.
      Never stop learning
      Basic LCD TV and Monitor troubleshooting guides.
      http://www.badcaps.net/forum/showthr...956#post305956

      Voltage Regulator (LDO) testing:
      http://www.badcaps.net/forum/showthr...999#post300999

      Inverter testing using old CFL:
      http://www.badcaps.net/forum/showthr...er+testing+cfl

      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
      http://s807.photobucket.com/user/budm/library/

      TV Factory reset codes listing:
      http://www.badcaps.net/forum/showthread.php?t=24809

      Comment

      • forswitch38
        Member
        • Sep 2015
        • 10
        • USA

        #4
        Re: Monitor: Sony SDM-HS74P LCD

        It's at a stupid angle and hard to get a good picture. I may try this weekend.

        I've been reading about switched mode power supplies:
        https://www.mikesarcade.com/cgi-bin/...e=psrepair.txt

        It mentions in there that switching transisters can "short-circuit, causing
        massive amounts of current to be drawn across the transformer and blowing
        the fuse." It says this often happens if the capacitors are bad.

        Can the switching transisters be damaged if the capacitors fail?

        Is there a way to guess what might cause the monitor to "display" this behaviour? The fact it's able to display correctly for a second or two after I turn it on leads me to believe something is working. And the fact ti passes the flash light test means the processing unit is working and activating the correct pixels, even after the fail condition occurs.

        I'm led to believe at this point the invertor and/or the CCFL's and/or wiring inbetween is the culprit. Can anyone elaborate on that?
        Last edited by forswitch38; 10-02-2015, 09:18 PM.

        Comment

        • forswitch38
          Member
          • Sep 2015
          • 10
          • USA

          #5
          Re: Monitor: Sony SDM-HS74P LCD

          Originally posted by budm
          You should also check those two blue caps next to the Inverter transforemrs and same for the two transistors (c5706/5706) next to the blue caps.
          This series are also known for having bad lamp assemblies.
          http://s807.photobucket.com/user/bud...?sort=3&page=1
          http://s807.photobucket.com/user/bud...?sort=3&page=1
          http://s807.photobucket.com/user/bud...?sort=3&page=1
          Thanks for the reply. I don't think I looked at them, but they may have been covered. You have to realize by now I'm completely noob with no tools atm. Information gathering right now because it's all I can do and need to do it anyway.

          These're "switching transisters"? Could I visible see any damage?

          By "lamp assembles" do you mean the ccfl's? How many are there? Four?
          Last edited by forswitch38; 10-02-2015, 09:21 PM.

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #6
            Re: Monitor: Sony SDM-HS74P LCD

            There are transistors that drive the high Voltage transformers to light up the lamps. You have to use meter to test them.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment

            • forswitch38
              Member
              • Sep 2015
              • 10
              • USA

              #7
              Re: Monitor: Sony SDM-HS74P LCD

              Anybody know by looking at the image of the board layout if there're "bleeder resistors" for the capacitors?


              If you're wondering what I mean, look here:
              https://www.youtube.com/watch?v=C7qnNMM7Dic

              See, I do not have a hand made bleeder resistor for discharging. I do have a screwdriver, naturally. I haven't plugged my monitor in for a couple days. That should be enough time, given what I've read.

              Anybody have a suggestion for a capacitor testing tool? I've read that ESR meters are the best for these switching power supplies. I've read about capacitance meters as well. Anyone offhand know hte difference?

              Would this do the job for measuring ESR:
              http://www.newegg.com/Product/Produc...4349-_-Product

              I hate the price, though, but... Anything else out there?

              Is there anyway I can use this analog multimeter for testing capacitors:
              http://www.ps2netdrivers.net/manual/...mt-12a/#manual
              Last edited by forswitch38; 10-03-2015, 04:21 PM.

              Comment

              • budm
                Badcaps Legend
                • Feb 2010
                • 40746
                • USA

                #8
                Re: Monitor: Sony SDM-HS74P LCD

                You can just measure the DCV between the two legs of that main filter cap to see what DCV you have left on the cap. If you do not have soldering iron to remove the suspected bad parts to test them off the board then you will need to have soldering iron and the solder removing tools. Cheaper to just replace the caps than trying to find out which one had bad ESR. You can buy cheap meter that will do resistance, ESR, DIODE TEST, ETC, READ THIS THREAD FOR EXAMPLE:
                https://www.badcaps.net/forum/showthread.php?t=49296
                Last edited by budm; 10-03-2015, 06:27 PM.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment

                • Joe Black
                  eager to learn
                  • Sep 2015
                  • 173
                  • southeastern europe

                  #9
                  Re: Monitor: Sony SDM-HS74P LCD

                  Originally posted by forswitch38
                  I'm led to believe at this point the invertor and/or the CCFL's and/or wiring inbetween is the culprit
                  Correct.

                  Basically, what Budm said. You'll HAVE to get a DMM and a soldering equipment if you want to work.
                  Don't discharge caps with screwdriver, just use common sense and don't touch anything dangerous. Hey, you'll most likely have to do some work with board plugged in, bleeder or not, so...

                  Ignore switching transistors. Check those budm pointed you to, and report back.
                  Correct checking procedure is easy to find on forums.
                  stay classy

                  Comment

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