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Fix for Benq FP737s 17" (Q7T3)

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    Re: Fix for Benq FP737s 17" (Q7T3)

    Originally posted by rbrt86 View Post
    Hello everyone,

    I really need your help. I've got a Benq FP737 with the same sympthoms as post #263: white backlight when monitor is off

    The blacklight used to be broken but then I:
    1) replaced the picofuse
    2) replaced the 4 c5707 transistors
    3) replaced the fu9024 fets

    Now the monitor works but smells like smoke and the backlight is white when off

    I noticed that one of the fu9024 fets gets really hot
    Is it a short circuit?

    Please help, your advice is very much appreciated!!

    Did you also remember to resolder all the transformer pins?

    Comment


      Re: Fix for Benq FP737s 17" (Q7T3)

      My FP737S has 2SJ598s in Q743 and Q 751.Is it ok to replace them with FU9024Ns?
      All transformers resoldered.all 2SC5707s replaced and bulging caps done(nearly all of the 470uf 35v ones)
      Smiffy

      Comment


        Re: Fix for Benq FP737s 17" (Q7T3)

        Originally posted by Smiffy View Post
        My FP737S has 2SJ598s in Q743 and Q 751.Is it ok to replace them with FU9024Ns?
        PlainBill answered this ...

        https://www.badcaps.net/forum/showpo...7&postcount=20
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        Comment


          Re: Fix for Benq FP737s 17" (Q7T3)

          Thanks RetiredCaps

          Smiffy

          Comment


            Re: Fix for Benq FP737s 17" (Q7T3)

            Hai Everybody,

            I joined in this forum yesterday. It is a very useful and helpful one. I could get some essential information regarding my damaged Benq LCD Monitor. Could somebody give the values of Caps @ C501 and C509 in Benq Q7C5 Power Supply Inverter Board? Thanks....
            Last edited by balu; 11-05-2011, 02:16 AM. Reason: Mistake in model No.

            Comment


              Re: Fix for Benq FP737s 17" (Q7T3)

              LCD monitor manufacturers use various power supplies and inverter boards for monitors with the same model number. You will need to open up the monitor and then you will be able to read the values of the needed capacitors. Many members here recommend replacing all of the electrolytic caps at the same time (except for the large main filter cap). There are several threads on here about ordering capacitors and recommended brands. If you make a list of the capacitors that are on your board, and list what replacement caps you think you should order, someone here can verify if you are ordering the right ones. Pictures also help people help you, use the manage attachments below the text area when posting through advanced messages.

              Comment


                Re: Fix for Benq FP737s 17" (Q7T3)

                hi, please help me with a problem, i have a benq FP731 monitor with a strange problem,
                the screen is white and nothing is displayed, only a few small lines colored.
                i have try to press and the ribbon from the lcd panel to logical board, but nothing.
                the monitor enters in standby or exit from standby when i disconect the input cable.

                any ideea where is the problem?

                Comment


                  Re: Fix for Benq FP737s 17" (Q7T3)

                  Originally posted by soulraven View Post
                  the screen is white and nothing is displayed, only a few small lines colored.
                  1) You could have a blown SMD fuse on the panel card that runs the length of the monitor. The panel card is usually at the top of the monitor.

                  2) There could be a bad voltage regulator on the main board.

                  3) You could have bad, but not bloated, caps on the main board.
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                  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.

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                  Comment


                    Re: Fix for Benq FP737s 17" (Q7T3)

                    thx,
                    i have check the fuse from the lcd panel and is ok,
                    but after that i have power again the monitor and is just work, no white screen, just work, but after a few hours or running ok, after i reconnect the monitor to power i get again the white screen. The last thing that i have work on it is the connector from the panel and the logical bord.
                    After that i have try again to check the connector, to check again the connection but nothing, still withe screen

                    any idea what about that? strange thing

                    Comment


                      Re: Fix for Benq FP737s 17" (Q7T3)

                      Hi check the fuse again - if you can get to it, try very gently pressing on it ( With something insulated )while everything is switched on -may be bad contact?
                      If it is a flat cable connector did you clean it. If it is pins have you checked for bent or broken pins.
                      "the monitor enters in standby or exit from standby when i disconect the input cable."

                      Do you mean the input from the PC - you should not plug/unplug any internal cables when it is switched on.
                      Please upload pictures using attachment function when ask for help on the repair
                      http://www.badcaps.net/forum/showthread.php?t=39740

                      Comment


                        Re: Fix for Benq FP737s 17" (Q7T3)

                        i will check the fuse again tomorow
                        "the monitor enters in standby or exit from standby when i disconect the input cable."
                        i mean the d-sub cable between pc and monitor

                        Comment


                          Re: Fix for Benq FP737s 17" (Q7T3)

                          i have check the fuse and nothing, i also measured and is ok.
                          i am sure that a imperfect contact somewhere. any idea about that? or something to measure and determine if everything is ok?

                          Comment


                            Re: Fix for Benq FP737s 17" (Q7T3)

                            Hi all,

                            I have 2 Benq FP737s, 1 work's perfectly well the other well I'll elaborate...

                            When switched on the LED will light up green but the backlight will flick on and off randomly, the signal/picture is still there as when it's flickering on and off if you shine a light on it you can still see the image.

                            So it hasn't completely died yet. I have searched this thread and apologise in advance if these symptoms have been seen before.

                            Thanks in advance.

                            Nick

                            Comment


                              Re: Fix for Benq FP737s 17" (Q7T3)

                              Hi All
                              New guy from Mozambique,
                              MAN! I wish I had a Pinch of the Knowlwdge floating around this forum, Good going Guys.
                              I have a Benq Q7T3 which has been good for years, now it has died a quiet death.
                              No lights no nothing, have done a cursory test of trannies and such, resoldered all joints, did not remove solder just resoldered and nothing happens.
                              I am a hobbyest and don't know much, am also 1000Km from civilization and batle to get spares quickly, have to wait till I go go to South Africa from time to time to purchase.
                              Please tell me where to start to look for the problem, I do have the diagram and understand a bit about testing.
                              Any help will be much appreciated
                              Kind Regards

                              Comment


                                Re: Fix for Benq FP737s 17" (Q7T3)

                                Hi,

                                Thanks for the info in this thread, it saved me a screen! (Though I was thinking of buying a new HUGE one already... damn...)

                                I have two HP 1740, one of them first was not able to switch off the backlight (nice LCD-going-off effect, then white), then after a week it died completely.
                                It has inside a derivative of the Q7T3 board (48.l1g02.a01) for which I could not find an exact schematic... (annoying!) It is slightly different since it does not have the PF751 (Vinverter fuse). What happened is one of the MOS switches (FU9024) blew to short (that's probably the screen not going off anymore?) and one of the bipolar c5707 blew as well (that's the screen dying I guess).

                                I got a repair kit from ebay, replaced all transistors (4 c5707, 2 FU9024), replaced the (only) fuse PF701 (that's the fuse before the large diodes with heatsink) and it worked! Tadaaa!

                                Thanks again! I just wonder how much longer these old screens will live (so I can finally buy myself something bigger )

                                Kuba

                                BTW. I also resoldered the inverter's transformers. It indeed looked like there is some wear on the joints...
                                Last edited by ronszon; 11-06-2012, 03:17 PM. Reason: update

                                Comment


                                  Re: Fix for Benq FP737s 17" (Q7T3)

                                  Hi,
                                  I just joined this forum, and have read through numerous posts to try and fix my Q7T3 Benq monitor.

                                  I have been getting the "2 seconds to black" problem. Although, at first, after switching the monitor off and on a number of times, it would work OK.

                                  There's nothing immediately apparent on the board itself. So, I tested the following, but replaced them anyway...

                                  1) the 3A picofuse
                                  2) the 4 2SC5707 transistors
                                  3) the 2 FU9024N fets

                                  ... but no difference.

                                  I have just retouched the solder on the inverters, and still no change... at first, anyway. After switching the monitor on and off a few times, I now get the Benq logo flashing every second or so.

                                  So, any ideas where I go from here, please?

                                  I also read that the octocoupler might need resoldering. Is this IC602 on my board? [48-L8302-A30].

                                  I'm fairly new to a lot of this stuff, so thanks for any help.
                                  Attached Files

                                  Comment


                                    Re: Fix for Benq FP737s 17" (Q7T3)

                                    Re touching may not be enough - You need to get some leaded solder to mix with the old solder then remove it -or most of it then resolder with new solder.
                                    Please upload pictures using attachment function when ask for help on the repair
                                    http://www.badcaps.net/forum/showthread.php?t=39740

                                    Comment


                                      Re: Fix for Benq FP737s 17" (Q7T3)

                                      IC602 probably is - re solder it anyway wont do any harm 4 legs? cant see it on pic.
                                      You should aso resolder those gray box caps with a k on between the 5707s and also the blue ceramic caps - and the inverter transformers and main transformer in fact if your good at soldering solder as much as you can be bothered with.
                                      Last edited by selldoor; 03-21-2013, 09:02 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: Fix for Benq FP737s 17" (Q7T3)

                                        Sch:
                                        The inverter transformer driving circuits are setup as self Osc Royer OSC, if the MOSFET which is PWM driven at the Gate to provide variable DC (more dc more brightness) for the Royer Osc, if the MOSFET shorted out (jump Source and Drain), the inverter will be running at full mode disregarding the PWM IC is working or not.
                                        Attached Files
                                        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


                                          Re: Fix for Benq FP737s 17" (Q7T3)

                                          Originally posted by selldoor View Post
                                          IC602 probably is - re solder it anyway wont do any harm 4 legs? cant see it on pic.
                                          You should aso resolder those gray box caps with a k on between the 5707s and also the blue ceramic caps - and the inverter transformers and main transformer in fact if your good at soldering solder as much as you can be bothered with.
                                          OK, thanks.

                                          IC602 does have 4 legs.

                                          Will resolder all, and report back...

                                          Comment

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