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LCD 19" BENQ T905 problems

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    Re: LCD 19" BENQ T905 problems

    ok thanks guys, now i need to get some equipment and spare parts
    Last edited by manthi; 02-26-2014, 01:58 PM.

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      Re: LCD 19" BENQ T905 problems

      Originally posted by manthi View Post
      so
      q808 and q809 give me reading of
      leg1 to leg 2 03.4
      leg1 to leg 3 03.0
      leg2 to leg 3 00.8

      q815 and q816
      leg1 to leg 2 1
      leg1 to leg 3 1
      leg2 to leg 3 1

      q805 and q812
      leg1 to leg 2 1
      leg1 to leg 3 1
      leg2 to leg 3 1

      so if i understand this correctly, my pico fuse pf801 is dead so are q808 q809
      and c826 has a broken soldering ,
      am i right, what else?
      You dont actually say what your meter was set on if 200ohms then 808 and 809 are off but assuming the "1" is on the left of the meter screen indicating over scale then q815 q816 q805 and q812 are good.
      If you are ordering get at least 2 extra. As already said it best to resolder ALL the high voltage joints - suggest remove as much of the old solder as you can and replace with fresh leaded solder.
      Please upload pictures using attachment function when ask for help on the repair
      http://www.badcaps.net/forum/showthread.php?t=39740

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        Re: LCD 19" BENQ T905 problems

        Originally posted by selldoor View Post
        You dont actually say what your meter was set on if 200ohms then 808 and 809 are off but assuming the "1" is on the left of the meter screen indicating over scale then q815 q816 q805 and q812 are good.
        If you are ordering get at least 2 extra. As already said it best to resolder ALL the high voltage joints - suggest remove as much of the old solder as you can and replace with fresh leaded solder.
        yes it was set at 200 ohm.
        when you say [resolder ALL the high voltage joints ] do you mean the 4 inverter transformers t801-802-803-804?

        i am going to practice soldering on a scrapped board, and see how it goes.
        what material should i buy?
        http://www.canadiantire.ca/en/tools-...soldering.html

        Comment


          Re: LCD 19" BENQ T905 problems

          Originally posted by manthi View Post
          when you say [resolder ALL the high voltage joints ] do you mean the 4 inverter transformers t801-802-803-804?
          Have you not read this thread it is mentioned over and over again
          Recently post 145 and 153
          Please upload pictures using attachment function when ask for help on the repair
          http://www.badcaps.net/forum/showthread.php?t=39740

          Comment


            Re: LCD 19" BENQ T905 problems

            Originally posted by selldoor View Post
            Have you not read this thread it is mentioned over and over again
            Recently post 145 and 153
            yes i read the entire thread, but for a novice like me, all those name transformer/inverter/caps/mosfet/capacitor diode..etc it get confusing.
            it is easier to understand if for exemple you say check pf801
            or resolder c824 c826 , then i know what you are talking about,
            anyways no matter what, all of you are of a great help, i sure couldn't fix that screen without your help

            Comment


              Re: LCD 19" BENQ T905 problems

              i bought a 25w weller iron,
              i removed pf801, it is dead
              removed q808 q809, one is dead but the other one looks good, when test it i get same result than q815 q816 (over range)
              i resolded the c826 leg,
              now i need to buy the 3a 125v fuse and the c5707 , couldn't find them at my local store, so i am going to order them from ebay,
              so it's going to take at least 2 weeks to arrive
              i will post an update
              Attached Files

              Comment


                Re: LCD 19" BENQ T905 problems

                You should replace the 5705s in pairs even if one is ok it is likely to go when paired with a new one. That is why I said order extras.
                2 weeks will give you lots of time to practice soldering and learn what the parts
                are called. We cant always see the numbers

                You REALLY do need to resolder ALL if you dont the 5707s will blow within a week
                (often quicker)
                Last edited by selldoor; 02-28-2014, 08:08 AM.
                Please upload pictures using attachment function when ask for help on the repair
                http://www.badcaps.net/forum/showthread.php?t=39740

                Comment


                  Re: LCD 19" BENQ T905 problems

                  i ordered a kit 4x c5707 2x fu9024n 1x 3a 125v fuse,
                  so it should be enough to replace my parts even if i damage one or two, the fuse is the only piece i don't have any spare, but my local store has it (the only part he has actually).
                  so time to practice now

                  Comment


                    Re: LCD 19" BENQ T905 problems

                    hey looks like it's working.

                    i replaced the 2 c5707 and the pico fuse, and the problem is gone.
                    but now i have the most challenging part to do, if i want to do a proper job

                    Originally posted by Krankshaft View Post
                    My standard operating procedure with these monitors is:
                    • Replace all of the secondary caps.
                    • Desolder all 4 inverter transformers legs and reflow them with new solder.
                    • Desolder all 4 transistors and the polyester caps (between the transistors) and inductors (nearby the transistors) for the inverter and reflow them.
                    • Check the rest of the board over with a magnifier for other bad joints.


                    If you haven't done all 4 steps in the list you will have a repeat failure.
                    since soldering is not my specialty, i am afraid that by trying to unsolder and redo all of the above steps, i might to more bad than good.
                    if i look at Capullaco story i think that is what happen to him
                    he bite off more than he could chew, and ended up with a big spark, and a dead lcd.
                    what do you think i should do the required steps and risk a total failure, or take a chance and leave the job as is (2 new c5707 1 picofuse and resolded polyester caps)

                    and a BIG THANKS to all the people that contributed to this thread, it is always fun to learn new things, in the end, it cost me more than buying a used lcd, but learning something knew is priceless
                    Attached Files

                    Comment


                      Re: LCD 19" BENQ T905 problems

                      I just repaired a Dell E173FPb (Benq board) that had one shorted 2sc5707, and the cause was poor solder connections on components in the inverter, (transformer and cap. c735) plus other misc. poor connections. check the connections with a magnifier, I use an old eye piece from an old camcorder, but any magnifier will help, just look for what looks like a small dark circle around the components lead where it is soldered, and just resolder it. They will look something like this more or less
                      Attached Files

                      Comment


                        Re: LCD 19" BENQ T905 problems

                        Hello everyone

                        First say that I am from Spain and sorry for my English , I am using google translator.
                        My monitor is a Benq T905 . Has the problem of two seconds and off . If I connect it to pc , I see the desktop and two seconds and off, after shotdown continuous green LED and shortly after passing yellow

                        With a multimeter checked

                        Picofuse (PF801*) = 0.04 ohms, ¿Is good?
                        Two C5707 = Bad
                        Two D10PF-06-6K036534 (Q812* - Q805*) = Bad

                        *See Photo

                        I have doubts:

                        ¿Where to buy or compatible D10PF-06-6K036534?, I do not find
                        What Picofuse buy considering that I live in Spain ( 220V ) ? This is good for me?--->Fuse3A 125V. Reading the post 99...Yes, I think so

                        First photo.....

                        Green star = Changed
                        Yellow star = Good
                        Red star = Bad

                        I will change the yellow and red stars , but any suggestions? (Also I will review welds as stated in the manual....A guide on how to troubleshoot 2 seconds to black)

                        Second photo....

                        Is the pic not find it anywhere , any equivalent ?

                        Wrote the best I could , thanks for your time and work. A greeting
                        Attached Files

                        Comment


                          Re: LCD 19" BENQ T905 problems

                          D10PF-06-6K036534 is probably:

                          std10pf06

                          Comment


                            Re: LCD 19" BENQ T905 problems

                            Hello group, I've got the 48.L1J02.A02 board which blows fuses (the main 2A one) - I found one leaking capacitor (C605 - 100uF/450V) but this couldn't be shorting, could it? When removing it one leg simply fell away.. What else should I be looking at? I use this schematic. Things before the 4 diode Graetz rectifier are OK. I suspected the rectifier itself but it also seems OK. Right after the rectifier the best looking candidate seems the Q601. Is the STP7NK80ZFP "Power MOSFET" (on the schematic called Q601 - 2SK3264) a typical failure? How to check it. What the ohmmeter should show? Every bit of help appreciated.
                            Last edited by silverdr; 04-25-2016, 04:00 PM.

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