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    #1

    L1975NW Issues...

    Hello all, noobie here.


    Well let me start by saying I searched about on here for my problems but found them to not be related to what I have.

    I bought this monitor for 200 back in 07-08ish and love this thing to death (I know right? I bet you will tell me otherwise) however, being pretty much problem free up until now it FINALLY gave up. I know these and some other related monitors have the common issue with the inverter, I don't think that is my problem.

    SO, I turn it off last night (nothing wrong with it at all, just another day), go to bed, then when I woke up to turn it on this morning, I got nothing. So I unplug it for a while, and come back to it. Plugged it back in and got nothing again. The light will be amber for a split second then either turn off or get VERY dim, and does it each time I plug it in and does not blink continuously. So since it is out of warranty i'm on my own and get it apart.

    What it does:
    Going through the basic things like looking the the MOSFETS and caps, some are starting to bulge but none are blown. The MOSFETS are not overheated and the F200 fuse is not blown either. Looks brand new, not even dust on it.

    Next I started to unplug the CCFL's, now the power LED gets brighter, plugged them back in and it got VERY dim, you can hardly see it. Unplugged them again and it got brighter. Then I started to remove the ribbon cables for the LCD controller, and as I removed BOTH of them the power LED was back to normal brightness, put them back and got dim again. Also the power button does nothing, I get NO response from it at all, and the screen will not show a signal so it's not bad backlights I don't think.

    Now I read up on the pins to the mainboard to the right of the inverter/power board and found a ground pin, a +5V and a +13.8V pin. When I tested for power I got 4.76 for the +5v and NOTHING for the 13.8V pin. I put the lamps back on the board and also the ribbon cables, tested them again, and the +5v was down to around 3v and again nothing for the 13.8v.

    So i'm not sure if that is normal, or what board is the bad one. Worked fine, no problems to this in about 9 hours. So that is when I decided to ask you guys before I toss about $90 into this for BOTH boards. Some of you know these things inside and out and I am ok with testing with a multimeter.

    Now up to you guys for help , outside of badcaps there in not a lot of info on this as far as I searched.
    Tags: None
    #2
    Re: L1975NW Issues...

    Originally posted by Alias View Post
    Going through the basic things like looking the the MOSFETS and caps, some are starting to bulge but none are blown.
    When caps are starting to bulge or already bulged, they are already bad. If your caps look like this

    https://www.badcaps.net/forum/attach...4&d=1281732206

    You won't get secondary voltages like 13.x V DC if the caps are bad. Also 4.76V DC on the 5V is low as well. If you replace the caps on the 5V rail, I bet that the readings will be > 5.00V DC.

    So first step is to make a list of ALL the caps, excluding the big one, which rarely, but not never, fails. Then order replacement Panasonic FR or FM or FC (in that preference) caps from digikey.com. After that, your monitor will likely work.
    Last edited by retiredcaps; 10-03-2011, 09:14 PM.
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      #3
      Re: L1975NW Issues...

      So it would be very unlikely for the mainboard to go out after something like this? If the caps are bad then that is no biggie for me, been there done that, but there being nothing on the 13.8 pin is what worries me.

      I'll go make a list or find one that is already been posted that is good.

      Thank you for the help

      Comment

        #4
        Re: L1975NW Issues...

        Originally posted by Alias View Post
        So it would be very unlikely for the mainboard to go out after something like this? If the caps are bad then that is no biggie for me, been there done that, but there being nothing on the 13.8 pin is what worries me.
        Your mainboard is likely okay.

        Let me guess. The caps that are bulging are likely marked 25V? If yes, that is why you get nothing on the 13.8V rail.
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          #5
          Re: L1975NW Issues...

          Originally posted by retiredcaps View Post
          Your mainboard is likely okay.

          Let me guess. The caps that are bulging are likely marked 25V? If yes, that is why you get nothing on the 13.8V rail.
          Umm, LOL must be more common then I thought.

          Comment

            #6
            Re: L1975NW Issues...

            Uhh sorry for reviving my old thread, but I finally got the parts and replaced the caps with a kit I bought. All rubicon caps installed and I ran into an issue. The screen used to turn on but no backlight but I could see the image with a light. Replaced all three of the fuses and the mosfets and now it power cycles on and off. The lamps do turn on for a split second but then it shuts off. Even with the lamps disconnected it still does it. I get 5V and 14.5-15 or so on the 13.6 lines even while it does this. But i'm kind of lost as none of the fuses are blown.

            Any idea on what is causing this? Thanks
            Last edited by Alias; 01-27-2012, 10:06 PM.

            Comment

              #7
              Re: L1975NW Issues...

              Originally posted by Alias View Post
              Any idea on what is causing this? Thanks
              Post top down view pictures of your all boards (both sides) following the instructions below exactly (in my sig file in post #2). Make sure to get at least one shot showing the new caps from the side so we can see if the Rubycon caps are real or fake (Rubycon is spelt with a "y").
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                #8
                Re: L1975NW Issues...

                Wow I did spell it with an I....

                They are "Rubycon" caps, and the are the 25V 1000uF caps. The other caps are black and gold with [M] on them (Panasonic FM's). ANYWAY, my camera will not focus on it at all and same with my phone.

                I did get it to do the 2 seconds to black last night and not just flicker on and off, but after 3 minutes it went right back to the flickering. That was after I left it alone unplugged for a while. Tried it again this morning and it's still flickering so I'm not sure what it's doing.

                I will try again with the pics on another camera.

                *update* Ok so I have found out that something on the circuit with the F200 fuse is still bad. When the fuse is blown the screen works, just no back lights and no power cycling. However to test I bridged the bad fuse and it went right back to the power cycling, removed the bridge and it turns on but no light.
                Last edited by Alias; 01-28-2012, 12:54 PM.

                Comment

                  #9
                  Re: L1975NW Issues...

                  Sorry for the double post, but it will not let me edit my last one.

                  I had it fixed for all of 5 minutes, I was all exited that it was working again and then all of a sudden the back lights went out again. I DID find out the problem component though, Q206; the top MOSFET. I still had the old two I replaced with then new ones. I changed the FET and worked fine for 5 minutes, then it shorted out just like the last one. Fuse is still there though so I'm puzzled now. I'll try another and see if it does the same thing.

                  Any ideas, cuz I'm out of them .

                  Comment

                    #10
                    Re: L1975NW Issues...

                    Originally posted by Alias View Post
                    Any ideas, cuz I'm out of them .
                    Pictures!
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                      #11
                      Re: L1975NW Issues...

                      Tried like 50 times for these....

                      The FET standing up is the one that keep going out. After 7 or so seconds of being on it gets very hot, the other one is not getting hot at all.

                      And yes go ahead and laugh at my soldering, I have no idea where my small tip is for my iron....
                      Attached Files
                      Last edited by Alias; 01-28-2012, 04:00 PM.

                      Comment

                        #12
                        Re: L1975NW Issues...

                        1) Hmm, C204 laying on its side says GL. I think that is a Capxon GL. Did you not replace this cap?

                        2) We usually recommend replacing mosfets in pairs. Did you test the bottom mosfet for shorts?

                        Here is how I test it (see section on mosfets).

                        https://www.badcaps.net/forum/showpo...4&postcount=19

                        You might as well test the top one too. Report your measurements for both mosfets.

                        3) That white glue can be removed. It is from the factory during assembly process to hold the components in place. After time, it can turn brown and be conductive.

                        4) I won't make fun of the soldering, but big blobs like that can lead to cold joints, solder bridges, etc which might be contributing to the problem.

                        5) Were the little caps southwest of the the big yellow transformer changed as well?

                        6) On a side note and for future readers, without pictures of your boards, I wouldn't have noticed #1, #3, #4, and #5.

                        7) Please retest all your fuses. A good fuse should measure less than 1.0 ohms.

                        8) You can also try to resolder/reflow the two blue caps to the right of the inverter transformer. You can also try to resolder/reflow all the inverter transformer pins. You may have to scrape away the glue from the factory. The reason for this suggestion is that some power boards like Benq are notarious for bad inverter transformer solder joints which causes the fets, transistors, fuses to go bad. It is a long shot with these Delta boards, but maybe worth trying?
                        Last edited by retiredcaps; 01-28-2012, 04:47 PM.
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                          #13
                          Re: L1975NW Issues...

                          Lots of threads regarding this board - when I saw the pic I thought here we go again. Anyway for what its worth I have read that among other things resistor R210 is a frequent cause of problems so needs to be tested.
                          Please upload pictures using attachment function when ask for help on the repair
                          http://www.badcaps.net/forum/showthread.php?t=39740

                          Comment

                            #14
                            Re: L1975NW Issues...

                            Originally posted by selldoor View Post
                            when I saw the pic I thought here we go again.
                            See another reason to post pictures! It prompted selldoor to make a valuable contribution regarding R210.
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                              #15
                              Re: L1975NW Issues...

                              1. No the kit did not have it, but I can replace it if I need to.

                              2. The bottom mosfet tests fine and swiches like it should both in and out of circuit. I bought a pair and installed them, the first one to fry was from the new kit. The one standing is the third one installed, two failed from overheating.

                              3. Okay I can remove the white stuff

                              4. I will go get some solder wick and redo them (I know you had to giggle at LEAST from seeing all those).

                              5. No kit did not have those either. They seem okay though but can also replace if I need to.

                              6. Yeah I can understand that pictures speak a thousand words.

                              Man my soldering skills are so

                              Update - R210 tests 1000 ohms in the 2000 range.

                              Edit - Nope, says 1000 on the top, testing produced random results (900-300 and everywhere in between). I tested a few other resistors and all check out so the meeter is good.

                              Edit 2 - Wow, there are many resistors that dont even give me readings.....
                              Last edited by Alias; 01-28-2012, 05:21 PM.

                              Comment

                                #16
                                Re: L1975NW Issues...

                                Even if those unreplaced caps are "fine", I would still replace them. You already have some quality Rubycon and Panasonic (the [M]) caps. That is one reason I don't recommend buying "kits". You pay a premium compared to DIY and they sometimes don't have all the caps required.

                                What is the color code for R210? Does your multimeter reading match that code?
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                                  #17
                                  Re: L1975NW Issues...

                                  "What is the color code for R210? Does your multimeter reading match that code? "

                                  Its not colour coded its an SMD But it should be 10 ohms.
                                  Please upload pictures using attachment function when ask for help on the repair
                                  http://www.badcaps.net/forum/showthread.php?t=39740

                                  Comment

                                    #18
                                    Re: L1975NW Issues...

                                    Well, it's not 10 ohms LOL. Where does that resistor go to? Honestly if there is many failed SMD components I might as well buy a replacement board and replace the caps on it. As you can see my SMD skills are

                                    Comment

                                      #19
                                      Re: L1975NW Issues...

                                      Originally posted by selldoor View Post
                                      Its not colour coded its an SMD But it should be 10 ohms.
                                      You know if I went and reviewed all these Delta power board threads, I probably have participated and seen the answer to that. After a few hundred of "virtual" lcd monitor repairs, it is all a blur now.

                                      Thanks for helping out, selldoor.
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                                        #20
                                        Re: L1975NW Issues...

                                        So what is the voltage supposed to be on the FET? I'm guessing there is WAAAYY too much power going through it. I would think about 12V for the lamps? I'm still not getting why the fuse is not blowing when it's on if it's getting overpowered.

                                        Comment

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