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HP L1955 just died

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    #1

    HP L1955 just died

    Hi, my HP L1955 just died. Was using it and suddenly the display dimmed real low, then back a bit, then low, then brighter, then black. All black. I can barely make out 'CHECK VIDEO CABLE' after disconnected computer and turned on again. LED on front bottom right seems working normally. Just seems backlight is not coming on. There was no smoke or smell or buzzing or anything.

    Found this site and see other posts for same monitor. Opened up display and investigated the inverter board; I see no visual problems on front or back. Hoping someone can please view and give me advice please? The other video board also looks very good shape. Please help?

    high-res photo links:

    http://home.comcast.net/~currygoat66...5/IMG_0549.JPG
    http://home.comcast.net/~currygoat66...5/IMG_0550.JPG
    http://home.comcast.net/~currygoat66...5/IMG_0553.JPG

    Please note on back of board, the square and rectangular black chips are all in great shape. The photo makes one of them appear indistinct. There are no bubbles on top of these things.
    Attached Files
    Last edited by toshiba1; 09-26-2011, 08:30 PM.
    Tags: None
    #2
    Re: HP L1955 just died

    Please no inline images! Please use the attachments thumbnails, thank you!

    Comment

      #3
      Re: HP L1955 just died

      Use the search function I made a huge thread on troubleshooting the inverter section of this specific model monitor.

      https://www.badcaps.net/forum/showthread.php?t=8598
      Last edited by Krankshaft; 09-26-2011, 08:33 PM.
      Elements of the past and the future combining to make something not quite as good as either.

      Comment

        #4
        Re: HP L1955 just died

        I actually did read your repair guide (thanks for that). My board doesn't have an inverter fuse like the one in your picture. Mine is just a strip of metal. That's weird.

        I guess I need guidance. Even if there are no visual problems, I should replace components? Darn it, I love this monitor. :\

        Comment

          #5
          Re: HP L1955 just died

          So you are seeing a brief flash of the back lights on initial power up of the monitor?
          Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

          Comment

            #6
            Re: HP L1955 just died

            A bean counter probably eliminated the fuse brief flash with shut down is probably a bad C5707 inverter driver transistor check them for opens.
            Elements of the past and the future combining to make something not quite as good as either.

            Comment

              #7
              Re: HP L1955 just died

              <<So you are seeing a brief flash of the back lights on initial power up of the monitor?>>

              no, not seeing this. Just total black. I can barely make out 'CHECK VIDEO CABLE' with flashlight. Thanks.

              Comment

                #8
                Re: HP L1955 just died

                Originally posted by toshiba1 View Post
                no, not seeing this. Just total black. I can barely make out 'CHECK VIDEO CABLE' with flashlight. Thanks.
                Sounds like burned transistors in the inverter alright.
                Originally posted by PeteS in CA
                Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                A working TV? How boring!

                Comment

                  #9
                  Re: HP L1955 just died

                  <<Sounds like burned transistors in the inverter alright.>>

                  You are referring to the C5707? Will they look visibly burned? From Krankshaft's photo of where the 4 inverter transistors are located, they look perfectly fine. Those little plastic square things. They have C5707 on them. Should they visibly appear burned?? Thanks so much for your help on this.

                  <<transistor check them for opens.>>

                  I must admit I do not know what this means; maybe I'm in over my head. I can replace components though I'm pretty sure. Thanks for your patience.
                  Last edited by toshiba1; 09-27-2011, 07:30 AM.

                  Comment

                    #10
                    Re: HP L1955 just died

                    Originally posted by toshiba1 View Post
                    <<transistor check them for opens.>>

                    I must admit I do not know what this means;
                    See

                    https://www.badcaps.net/forum/showpo...0&postcount=13

                    specifically the section on "Multimeter" and "Shorted Transistors/MOSFETs".
                    --- 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

                      #11
                      Re: HP L1955 just died

                      Whew I just read the repair guide. I think it's unrealistic for me to have time to tackle this project. I guess I was hoping it would be an easy fix (i.e. an obvious bad capacitor and that was it).

                      If anyone wants to help, I would gladly drop some $ into your paypal account and mail away the panel to you. I would pay some reasonable fee for your expert analysis and repair. Of course I'm not sure if this is something people are open to doing normally. I really love this display, I don't want to recycle it. Well if anyone interested, please PM me.

                      Comment

                        #12
                        Re: HP L1955 just died

                        Just shotgun the components replace all four C5707s with new ones. Then check for bad cloudy or cracked solder joints on the inverter board and reflow them.

                        Attempt to power the monitor on by the rear switch then power it down by the front switch if the display shuts down when the front button is pressed but the backlight remains on. One of the two backlight 4 pin SMD FETs is shorted. They don't always fail and there is no harm in powering up to check if one of them failed. Replace both of them in that case.

                        In most cases this will restore the inverter to operation. All the troubleshooting work has been done for you.

                        I have a fully repaired and recapped spare power supply here from a junked 1955 that had a bad panel. I guess we could work out something for the broken board. But it's much more satisfying to repair it yourself.
                        Elements of the past and the future combining to make something not quite as good as either.

                        Comment

                          #13
                          Re: HP L1955 just died

                          Thx for the info Krankshaft.

                          Comment

                            #14
                            Re: HP L1955 just died

                            To Krankshaft and all the other contributors: You guys

                            I bought my L1955 used. It lasted for a couple of months and then died like so many others described in the forum. I had difficulty finding information on disassemby and repair. I was about to recycle it when I found disassembly instructions from HP and found this forum.

                            I've already replaced the 5707s and soldered the bad joints on the inverter board. There were so many bad joints that I'm suprised that it worked as long as it did. So I'm going to find out what else needs to be replaced and see what happens.

                            Thanks for sharing your knowledge and experience on the L1955 threads!

                            REK

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