Announcement

Collapse
No announcement yet.

Benq Inverter board C5707 Transistors

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Benq Inverter board C5707 Transistors

    Hello everyone,


    I have a faulty HP 1940 with a Benq 48.LIG02.A01 inverter board. It has the fault where it the screen goes black after a few seconds, after putting a flash light to it I could see that the image was still there. i Opened it up and inspected the inverter board I could not see any faulty caps and the soldering looks good to me (I'm a novice) so after reading through the posts here I decided to pull the four C5707 transistors off the board and test them with my DMM, as I have read here that these transistors are a common fault with this board. Because I have little experience testing transistors I was hoping for some conformation from the experts (you)


    I pulled 4 transistors off the board and kept them separated in pairs as I'm told the fail in pairs.


    The first pair gave me the following results (all tested with the diode function on my DMM)


    Transistor 1 (first pair)


    B-E .575 v
    B-C .575v
    C-E Open
    E-C Open


    Transistor 2 (first pair)
    Same as above


    Transistor 3 (second pair)
    B-E 0.00v (it did not read 0L )
    B-C .349v
    C-E .349v
    E-C .360v


    Transistor 4 (second pair)
    B-E 0.00v (it did not read 0L )
    B-C .444v
    C-E .478v
    E-C OPEN


    it seems to me that the second pair is faulty I was wondering if anyone can confirm this? I have found a place on ebay where I can order some new C5707s. Also As a precaution I have touched up the soldering on all the transformers in case this was the cause of the fault. Anything else I should check?


    Thanks heaps for all the great tips I found here I would never have tried this without the advice I have found on this site.

    I have also posted this on fixya hope you dont mind me posting this in more then one place.

    Mike

    #2
    Re: Benq Inverter board C5707 Transistors

    I'm normally on Fixya !

    I am still trying to get to the biottom of my dell E173FPb

    I bought 4 c5707 and the fuse from Ebay - replaced them anyway as the problem seemed only to occur when hot - and I couldn't test this.

    Checked for any cold joints around the transformers.

    Do your power transistors look hot - slight browning of the board around heatsinks ?

    Anyway - replaced the 4 + fuse - and still had same problem.
    Then replaced the major Elec' Caps - still same problem. I now suspect the 2 squat caps near the header to the small board. (on RHS next to inductor on photo below)

    From other forums and google pics - there are another 2 power transistors sitting on their in the centre of the board - marked on this photo in blue -
    http://www.ccl-la.com/images/LCD5_9.jpg

    May be worth pulling these too.

    Comment


      #3
      Re: Benq Inverter board C5707 Transistors

      2nd pair r faulty. cheers

      Comment


        #4
        Re: Benq Inverter board C5707 Transistors

        Originally posted by avsubvert
        Hello everyone,


        I have a faulty HP 1940 with a Benq 48.LIG02.A01 inverter board. It has the fault where it the screen goes black after a few seconds, after putting a flash light to it I could see that the image was still there. i Opened it up and inspected the inverter board I could not see any faulty caps and the soldering looks good to me (I'm a novice) so after reading through the posts here I decided to pull the four C5707 transistors off the board and test them with my DMM, as I have read here that these transistors are a common fault with this board. Because I have little experience testing transistors I was hoping for some conformation from the experts (you)


        I pulled 4 transistors off the board and kept them separated in pairs as I'm told the fail in pairs.


        The first pair gave me the following results (all tested with the diode function on my DMM)


        Transistor 1 (first pair)


        B-E .575 v
        B-C .575v
        C-E Open
        E-C Open


        Transistor 2 (first pair)
        Same as above


        Transistor 3 (second pair)
        B-E 0.00v (it did not read 0L )
        B-C .349v
        C-E .349v
        E-C .360v


        Transistor 4 (second pair)
        B-E 0.00v (it did not read 0L )
        B-C .444v
        C-E .478v
        E-C OPEN


        it seems to me that the second pair is faulty I was wondering if anyone can confirm this? I have found a place on ebay where I can order some new C5707s. Also As a precaution I have touched up the soldering on all the transformers in case this was the cause of the fault. Anything else I should check?


        Thanks heaps for all the great tips I found here I would never have tried this without the advice I have found on this site.

        I have also posted this on fixya hope you dont mind me posting this in more then one place.

        Mike
        You are correct as electroguy75 confirms, also check inverter fuse as it will probably be open
        When in circuit you measure pairs of C5707s, when one is open they will both read open
        When removed from board only one reads bad, usually,but its best to replace in pairs anyway
        As you have the pair bad you may find there may be a faulty CCFL or something else,check your solder joints carefully

        Comment


          #5
          Re: Benq Inverter board C5707 Transistors

          Originally posted by Richie_asg1
          I'm normally on Fixya !

          I am still trying to get to the biottom of my dell E173FPb

          I bought 4 c5707 and the fuse from Ebay - replaced them anyway as the problem seemed only to occur when hot - and I couldn't test this.

          Checked for any cold joints around the transformers.

          Do your power transistors look hot - slight browning of the board around heatsinks ?

          Anyway - replaced the 4 + fuse - and still had same problem.
          Then replaced the major Elec' Caps - still same problem. I now suspect the 2 squat caps near the header to the small board. (on RHS next to inductor on photo below)

          From other forums and google pics - there are another 2 power transistors sitting on their in the centre of the board - marked on this photo in blue -
          http://www.ccl-la.com/images/LCD5_9.jpg

          May be worth pulling these too.
          You seem to have done the ground work
          As you say this happens when hot, that sugests to me that you need to check out your CCFLs
          The 2 transistors you marked in blue turn the backlights off, when they go the backlights stay on when monitor is turned off

          Comment


            #6
            Re: Benq Inverter board C5707 Transistors

            If you can't get the original 2SC5707 transistors, you can use D44H11 transistors to do the job. They're in a TO-220 package though, larger than the original transistors, but they can probably still fit.

            My BenQ FP731 17" LCD monitor failed last year, after a long inspection I found that the 2SC5707 transistors had failed along with the fuse. Digikey doesn't have 2SC5707 transistors, so I ordered D44H11 transistors. My monitor still works good.
            My gaming PC:
            AMD Phenom II X6 1100T Black Edition 3.3GHz Six-Core CPU (Socket AM3)
            ASUS M4A77TD AMD 770 AM3 Motherboard
            PowerColor AMD Radeon RX 480 8GB GDDR5 PCI-Express x16 3.0 Graphics Card
            G.SKILL Value Series 16GB DDR3-1333 RAM (4x4GB dual channel)
            TOSHIBA DT01ACA200 2TB 3.5" SATA HDD (x2)
            WD Caviar Green WD20EARX 2TB 3.5" SATA HDD
            ASUS Xonar DG 5.1 Channel PCI sound card
            Antec HCG-750M 750W ATX12V v2.32 80 PLUS BRONZE Power Supply
            Antec Three Hundred Mid-Tower Case
            Microsoft Windows 10 Pro 64-bit
            Microsoft Windows 7 Ultimate SP1 64-bit

            Comment


              #7
              Re: Benq Inverter board C5707 Transistors

              Originally posted by Richie_asg1

              Checked for any cold joints around the transformers.
              Afterthought
              Its best to resolder the transformers as it is the ring cracks that you find with them
              As in this Link
              https://www.badcaps.net/forum/showpo...&postcount=231

              Comment


                #8
                Re: Benq Inverter board C5707 Transistors

                Thanks for the pointer BobDee - and Excellent photo by the way of cold solder cracking. Will resolder all transformer pins.

                My symptoms are- works fine daily - for an hour or more, then display goes black - green power button stays on. turn off, turn on - will stay on for a few seconds before going black again. Leaving to cool results in good working again.
                Display goes bright for 2 seconds before going black completely. Tried adjusting brightness - but has little effect. This rings a bell with something I've read - but can't remember which bit.

                I'm thinking a transistor is getting too much current - then crowbaring into full conduction - resulting in a shutdown. Possibly one of the limiting resistors - but which one ?

                Also I'm not too ok with working on live equipment to check working voltages. Is there a safer way of doung things besides being suspended by a rubber bungie rope?

                Cheers.

                Comment


                  #9
                  Re: Benq Inverter board C5707 Transistors

                  Originally posted by Richie_asg1
                  Thanks for the pointer BobDee - and Excellent photo by the way of cold solder cracking. Will resolder all transformer pins.

                  My symptoms are- works fine daily - for an hour or more, then display goes black - green power button stays on. turn off, turn on - will stay on for a few seconds before going black again. Leaving to cool results in good working again.


                  Cheers.
                  Do you get the odd flicker of backlights before they fail,
                  With the symptoms you mention above and the odd flicker of lights before failure sugest that its a faulty CCFL
                  They are worthy of a check to see if this is the problem as well as resoldering transformers

                  Never come across your sugestion of limiting resistors being the problem
                  These Benq boards are in Benqs + HPs + Dells etc I have done many ( 2 seconds to black problems ) as they are called
                  standard fix = replace faulty C5707s + pico fuse + resolder transformers, and check and resolder any other bad solder joints if that dont repair it then its usualy bad CCFLs

                  Comment


                    #10
                    Re: Benq Inverter board C5707 Transistors

                    Originally posted by Bobdee
                    Do you get the odd flicker of backlights before they fail,
                    With the symptoms you mention above and the odd flicker of lights before failure sugest that its a faulty CCFL
                    They are worthy of a check to see if this is the problem as well as resoldering transformers

                    Never come across your sugestion of limiting resistors being the problem
                    These Benq boards are in Benqs + HPs + Dells etc I have done many ( 2 seconds to black problems ) as they are called
                    standard fix = replace faulty C5707s + pico fuse + resolder transformers, and check and resolder any other bad solder joints if that dont repair it then its usualy bad CCFLs
                    No flicker - just bright for a second or two - then blackout.
                    I'll stick with replacing the last two 1000uf 10v caps I didn't have last time, testing those FU9024N transistors and resoldering the transformers complete.
                    Will also check the CCFL's when I read how to do that.

                    Will report back how things go. Thanks for your help again. Great forum - great people.

                    Comment


                      #11
                      Re: Benq Inverter board C5707 Transistors

                      Originally posted by avsubvert
                      Hello everyone,


                      I have a faulty HP 1940 with a Benq 48.LIG02.A01 inverter board. It has the fault where it the screen goes black after a few seconds, after putting a flash light to it I could see that the image was still there. i Opened it up and inspected the inverter board I could not see any faulty caps and the soldering looks good to me (I'm a novice) so after reading through the posts here I decided to pull the four C5707 transistors off the board and test them with my DMM, as I have read here that these transistors are a common fault with this board. Because I have little experience testing transistors I was hoping for some conformation from the experts (you)


                      I pulled 4 transistors off the board and kept them separated in pairs as I'm told the fail in pairs.


                      The first pair gave me the following results (all tested with the diode function on my DMM)


                      Transistor 1 (first pair)


                      B-E .575 v
                      B-C .575v
                      C-E Open
                      E-C Open


                      Transistor 2 (first pair)
                      Same as above


                      Transistor 3 (second pair)
                      B-E 0.00v (it did not read 0L )
                      B-C .349v
                      C-E .349v
                      E-C .360v


                      Transistor 4 (second pair)
                      B-E 0.00v (it did not read 0L )
                      B-C .444v
                      C-E .478v
                      E-C OPEN


                      it seems to me that the second pair is faulty I was wondering if anyone can confirm this? I have found a place on ebay where I can order some new C5707s. Also As a precaution I have touched up the soldering on all the transformers in case this was the cause of the fault. Anything else I should check?


                      Thanks heaps for all the great tips I found here I would never have tried this without the advice I have found on this site.

                      I have also posted this on fixya hope you dont mind me posting this in more then one place.

                      Mike


                      Hello, sorry I have not kept you updated with my progress. Thanks for your replies. I got called into another project so I had to put the monitor repair on hold for a while.

                      So after reading your replies about the transistors I order in some from farnell and installed them into the board. Touched up the solder on the transistors and checked the fuse. I replaced all 4 c5707's just to be sure. After turning on the monitor I was delighted to see that the back lights now comes on and stays on.

                      However when I connected a computer to the VGA input the monitor did not detect the signal. After turning it on the monitor gives the message after about 30 seconds: Monitor going to sleep and goes into standby. When I reset my computer the monitor came of standby for a second and displayed the monitor going to sleep message again... no image


                      is there something I could have done to damage the board as part of my repairs? How would I go about diagnosing this issue?


                      Thanks for all your help


                      Mike

                      Comment


                        #12
                        Re: Benq Inverter board C5707 Transistors

                        Originally posted by Newbie2
                        If you can't get the original 2SC5707 transistors
                        http://cgi.ebay.com/ws/eBayISAPI.dll...m=320310321434

                        http://cgi.ebay.com/ws/eBayISAPI.dll...m=160359156562
                        Mann-Made Global Warming.
                        - We should be more concerned about the Intellectual Climate.

                        -
                        Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.

                        - Dr Seuss
                        -
                        You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
                        -

                        Comment


                          #13
                          Re: Benq Inverter board C5707 Transistors

                          If you find what model Benq your inverter board is from and go here:- http://www.elbase.ru/app/webroot/files/cd/monitor/BENQ/ you may be able to find something to get you a stage further. There's a wealth of technical knowledge for loads of monitors on the site.

                          Comment


                            #14
                            Re: Benq Inverter board C5707 Transistors

                            Hello guys, my BenQ stopped working (lights won't start) the other day after doing a bit of on and off lasting a few seconds, then just dark. I stripped the board and found a pair of the C5707 conducting C-E, thus I replaced them with a pair of TIP3055 together with the 3A picofuse which wasn't working any more as well.

                            Turned on the monitor and seemed it was working, displaying BenQ's screen and then the motherboard boot after turning on the computer. Only a few seconds and it turned off, then on again and so on till I turned everything off before going back again to the previous stage ;-)

                            Do you have any hint? I only have a simple multimeter to test the components.

                            Thank you very much for your help.

                            Comment


                              #15
                              Re: Benq Inverter board C5707 Transistors

                              Originally posted by MarcoPau
                              Hello guys, my BenQ stopped working (lights won't start) the other day after doing a bit of on and off lasting a few seconds, then just dark. I stripped the board and found a pair of the C5707 conducting C-E, thus I replaced them with a pair of TIP3055 together with the 3A picofuse which wasn't working any more as well.

                              Turned on the monitor and seemed it was working, displaying BenQ's screen and then the motherboard boot after turning on the computer. Only a few seconds and it turned off, then on again and so on till I turned everything off before going back again to the previous stage ;-)

                              Do you have any hint? I only have a simple multimeter to test the components.

                              Thank you very much for your help.
                              The common problem with this inverter design is cracked solder joints around the the transformers. Since the TIP3055 has greater current capacity than the 2SC5707, you are probably overloading the power supply. I suggest resoldering every pin of both inverter transformers, then checking the transistors for shorts. If you STILL have the problem replace the transistors with good quality 2SC5707 (C5707).

                              PlainBill
                              For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                              Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                              Comment


                                #16
                                Re: Benq Inverter board C5707 Transistors

                                Originally posted by MarcoPau
                                Hello guys, my BenQ stopped working (lights won't start) the other day after doing a bit of on and off lasting a few seconds, then just dark. I stripped the board and found a pair of the C5707 conducting C-E, thus I replaced them with a pair of TIP3055 together with the 3A picofuse which wasn't working any more as well.

                                Turned on the monitor and seemed it was working, displaying BenQ's screen and then the motherboard boot after turning on the computer. Only a few seconds and it turned off, then on again and so on till I turned everything off before going back again to the previous stage ;-)

                                Do you have any hint? I only have a simple multimeter to test the components.

                                Thank you very much for your help.
                                I am not sure if this is the cause of your problem but as you did not replace with C5707s (that is considered the best for the job) with new C5707s, then you may need to replace the other two so as to have four TIP3055s to balance circuit(as TIP3055s are slower) Better still four C5707s as they are easily available on Ebay
                                Also did you resolder the four inverter Transformers, if not do so or you may end up with new failures in transistors and fuse

                                Comment


                                  #17
                                  Re: Benq Inverter board C5707 Transistors

                                  An interesting article on the Benq C5707 transistor problems.

                                  http://www.electronicrepairguide.com...or-repair.html

                                  Comment

                                  Working...
                                  X