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    GNR TS700 2 seconds to black

    This monitor was part of the bunch that I got today.

    The backlight would turn on and off every second or two. I took it apart and tried another set of CCFL's connected to the power supply ans it still did the same. 2 CCFL's would light up and 2 of them would not light at all.

    When I took it apart it was obvious that the 2 mosfets that drive one of the inverters were burnt out. I gave them a clean and tested them. They are both shorted.

    I have removed them and cleaned up the area ready for some new ones but I am struggling to find these transistors? anywhere.

    DK
    QJ

    Is all I can see on them but looking in all of the normal places returns no results.
    Attached Files
    Last edited by Jasgriff; 04-03-2012, 11:09 AM.
    Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

    How to resize your pictures guide click HERE
    Retiredcaps Ideal post example click HERE

    #2
    Re: GNR TS700 2 seconds to black

    I got the same problem with a Viewsonic VX724. DKQS was the name of my part and it was a 2SC4672.
    You should look for the datasheet of your board and make sure that is the same transistor (or bipolar).

    In my case, it was almost the same price of 5 transistors (because I had to import them) and a used (but working) board. So I obviously bought the board.

    Anyways, you can check this guide about 2 seconds to black: https://www.badcaps.net/forum/showpo...4&postcount=19 & https://www.badcaps.net/forum/showpo...4&postcount=20.

    Cheers.

    Comment


      #3
      Re: GNR TS700 2 seconds to black

      Just tried swapping the 2 working transistors to the other inverter and the CCFL attempts to light up on that side so hopefully that will mean that a couple of transistors will do the trick.
      Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

      How to resize your pictures guide click HERE
      Retiredcaps Ideal post example click HERE

      Comment


        #4
        Re: GNR TS700 2 seconds to black

        Originally posted by Nocta View Post
        I got the same problem with a Viewsonic VX724. DKQS was the name of my part and it was a 2SC4672.
        Made by Rohm. See

        https://www.badcaps.net/forum/showpo...80&postcount=9

        https://www.badcaps.net/forum/showpo...7&postcount=10

        2 for $2.50 + free shipping or 5 for $4.99 + free shipping on ebay. I would get the 5 and have a few spares.
        Last edited by retiredcaps; 04-03-2012, 02:14 PM.
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        Comment


          #5
          Re: GNR TS700 2 seconds to black

          Good point. I haven't looked for the transistor on eBay. I think I'll buy 5 of them so I can use 2 and sell the board. Plus, I have 3 spare transistors (just in case).
          I ordered the used board, though. It was not expensive so .... :P

          Comment


            #6
            Re: GNR TS700 2 seconds to black

            I wish that was the case for me!

            I have had a look at they are £2.49 each + £1.49 for postage. They are a real rip off.

            I had a look and found that someone couldn't sell the same monitor smashed for 99p so I have messaged them to see if they still have it. No point spending 6.49 on 2 components that cost 1/3rd of that price.
            Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

            How to resize your pictures guide click HERE
            Retiredcaps Ideal post example click HERE

            Comment


              #7
              Re: GNR TS700 2 seconds to black

              Originally posted by Jasgriff View Post
              I have had a look at they are £2.49 each + £1.49 for postage. They are a real rip off.
              Shows free shipping if I change country to UK

              http://www.ebay.ca/itm//270889006243

              http://www.ebay.ca/itm/390313925820
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                #8
                Re: GNR TS700 2 seconds to black

                Ahh so it does. I never thought of looking at a different country's ebay then changing it to uk. I have made an offer to this guy in the uk if that doesnt come off then I will order them from China Ta.
                Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                How to resize your pictures guide click HERE
                Retiredcaps Ideal post example click HERE

                Comment


                  #9
                  Re: GNR TS700 2 seconds to black

                  Ebay is a good place to do business with China because of the pay-pal. See if you can get the seller to sweeten the deal.. I mean these parts are cheaper then what they sell for in America.

                  Comment


                    #10
                    Re: GNR TS700 2 seconds to black

                    Transistors arrived and fitted this has not cured the problem. I need to crack it open again and take a look at what's going on.
                    Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                    How to resize your pictures guide click HERE
                    Retiredcaps Ideal post example click HERE

                    Comment


                      #11
                      Re: GNR TS700 2 seconds to black

                      1) Do the new mosfets test shorted?

                      2) Do the pins get any DC power?

                      3) Please post a picture of the top side of the power board.
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                        #12
                        Re: GNR TS700 2 seconds to black

                        Right the new mosfets don't test shorted but the working old ones that I moved to replace the broken ones are now shorted. nooooooooo another couple of wasted mosfets!

                        There are 2 diodes connected to these mosfets and the diode on the broken ones appears to be shorted. I am guessing this is what is breaking the mosfets?

                        I will get some pics in a bit.
                        Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                        How to resize your pictures guide click HERE
                        Retiredcaps Ideal post example click HERE

                        Comment


                          #13
                          Re: GNR TS700 2 seconds to black

                          Originally posted by Jasgriff View Post
                          There are 2 diodes connected to these mosfets and the diode on the broken ones appears to be shorted. I am guessing this is what is breaking the mosfets?
                          Probably. Desolder the diode and verify out of circuit that it is shorted.
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                          Comment


                            #14
                            Re: GNR TS700 2 seconds to black

                            Did you check the tuning caps? there should be caps on the top side of the board for this Royer Oscillator circuits.
                            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


                              #15
                              Re: GNR TS700 2 seconds to black

                              Desoldered the Diodes and they tested ok outside of the circuit. I desoldered the mosfets too and 1 of them seems ok whilst the other is shorted.

                              are the tuning caps the ones that are connected directly to the mosfets?
                              Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                              How to resize your pictures guide click HERE
                              Retiredcaps Ideal post example click HERE

                              Comment


                                #16
                                Re: GNR TS700 2 seconds to black

                                There should be a cap connected in parallel with the primary side of the inverter transformer. Do you have the picture of the top side of the board?
                                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


                                  #17
                                  Re: GNR TS700 2 seconds to black

                                  Il get the pic now.
                                  Attached Files
                                  Last edited by Jasgriff; 04-09-2012, 10:19 AM.
                                  Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                                  How to resize your pictures guide click HERE
                                  Retiredcaps Ideal post example click HERE

                                  Comment


                                    #18
                                    Re: GNR TS700 2 seconds to black

                                    The two blue caps in the top center of the picture. If they are off value then that will cause the Osc to run at the wrong frequency as designed and can cause the MOSFET to over heat or damaged.
                                    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


                                      #19
                                      Re: GNR TS700 2 seconds to black

                                      Right took them out to measure them.

                                      1 measures out of range and the other measure 340nf.

                                      7C224J is the model of the cap.

                                      I am guessing this is what could be causing the short?
                                      Fixed so far : 1 Home cinema system, 16 LCD Monitors, 4 LCD TV's

                                      How to resize your pictures guide click HERE
                                      Retiredcaps Ideal post example click HERE

                                      Comment


                                        #20
                                        Re: GNR TS700 2 seconds to black

                                        They are 0.22uF 5% (224J), at least 250v rating.
                                        One is reading 340nF (.34uF)? It does not have any resistance reading on this one?
                                        If they are not within 5% (J) then you do have problem and that can damage your new MOSFETs
                                        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

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