Fix for Benq FP737s 17" (Q7T3)

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • agentsmithitaly
    New Member
    • Feb 2008
    • 5

    #101
    Re: Fix for Benq FP737s 17" (Q7T3)

    Krankshaft thank you for the reply!

    I'm sorry if I haven't posted yet but the guys i bought the 2SC5705 shipped me the SMD version, so I had to wait they restock through hole version and sent me again.
    Well I replaced all the 5705's to be sure and the 3A fuse. The monitor worked for four days, I was so excited, then it faulted again.

    This time the CCFLs stay on only for half a second then they turn off. In this half second you can see the BenQ logo fading.
    Then the power led is still green but you can see nothing on the LCD, even with strong light pointed at it. Before repairing attempt I could see the picture with this solution.

    It seems that 5705 failed again (but no blown fuse) or they are ok and something else is faulty.
    What can I do? I could replace the small 945 and 733 transistor, but getting new mosfets or DQ10DPF could be too much expensive and not worthing the waste of time...

    Comment

    • agentsmithitaly
      New Member
      • Feb 2008
      • 5

      #102
      Re: Fix for Benq FP737s 17" (Q7T3)

      I forgot to say there is no bulging capacitors, and solder joints seem fine at my inexperienced eyes. How can I test the capacitors?

      Comment

      • Newbie2
        Badcaps Veteran
        • Sep 2005
        • 885
        • Canada

        #103
        Re: Fix for Benq FP737s 17" (Q7T3)

        Originally posted by agentsmithitaly
        I forgot to say there is no bulging capacitors, and solder joints seem fine at my inexperienced eyes. How can I test the capacitors?
        The quick blink seems to suggest a blown fuse as I did see that happen when I ran a BenQ monitor with good transistors but with a bad 3A fuse.

        A "slow blow" fuse is recommended for replacement of the small 3A fuse, if you are not using the "bel MS3" 3A fuse (the original fuse) you can order them off Digikey (Digikey part number: 507-1034-ND).

        Check solder joints and replace the fuse and transistors and see what happens.
        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

        • davmax
          Badcaps Veteran
          • Dec 2005
          • 899

          #104
          Re: Fix for Benq FP737s 17" (Q7T3)

          It is not a good idea to have a 3A slow blow fuse "not recommended if it is to protect the transistors". A fast fuse may save the transistors.

          agentsmithitaly

          I suspect blown transistors again.
          1. Make sure that all the inverter transformer connections are resoldered
          2. Use a fast 3A fuse
          3. Check the MOSFET in each circuit Q751 & Q743 (FU9024N) they should not read a short circuit.

          http://www.lcdrepair.us/fu9024n.html

          See my experiences earlier in the thread. These transistors are not well protected by the circuit design. I modified the circuit and the monitor is very well protected.
          Gigabyte EP45-DS3L Ultra Reliable (Power saver)
          Intel E8400 (3000Mhz) Bios temps. 4096Mb 800Mhz DDR2 Corsair XMS2 4-4-4-12
          160Gb WD SATAII Server grade
          Nvidia 8500GT 256Mb
          160Gb WD eSATAII Server grade for backup.
          Samsung 18x DVD writer
          Pioneer 16x DVD writer + 6x Dual layer
          33 way card reader
          Windows XP Pro SP3
          Thermaltake Matrix case with 430W Silent Power
          17" Benq FP737s LCD monitor
          HP Officejet Pro K5300 with refillable tanks

          Comment

          • davmax
            Badcaps Veteran
            • Dec 2005
            • 899

            #105
            Re: Fix for Benq FP737s 17" (Q7T3)

            Further note on fuses.


            My FP737s is working long term on a 3.15A quick blow fuse part 226-0787 from RS Electronic Components. Wickmann part 3951315000
            Gigabyte EP45-DS3L Ultra Reliable (Power saver)
            Intel E8400 (3000Mhz) Bios temps. 4096Mb 800Mhz DDR2 Corsair XMS2 4-4-4-12
            160Gb WD SATAII Server grade
            Nvidia 8500GT 256Mb
            160Gb WD eSATAII Server grade for backup.
            Samsung 18x DVD writer
            Pioneer 16x DVD writer + 6x Dual layer
            33 way card reader
            Windows XP Pro SP3
            Thermaltake Matrix case with 430W Silent Power
            17" Benq FP737s LCD monitor
            HP Officejet Pro K5300 with refillable tanks

            Comment

            • agentsmithitaly
              New Member
              • Feb 2008
              • 5

              #106
              Re: Fix for Benq FP737s 17" (Q7T3)

              Thank you guys for the suggestions. I'll check them out and let you know.

              If I understood the schematics correctly (btw i'm just a hobbyist), the 3A fuse provide current to power the inverter section, so blown fuse = no light, not even for half a second. am I right?


              Please notice that I never rebooted the pc in these four days before failing, just stand-by (yellow led) since i read the Davmax investigation about the BLT_ON issue, unfortunately the workaround is too complicated for my electronic skills to implement

              Comment

              • Newbie2
                Badcaps Veteran
                • Sep 2005
                • 885
                • Canada

                #107
                Re: Fix for Benq FP737s 17" (Q7T3)

                Originally posted by agentsmithitaly
                Thank you guys for the suggestions. I'll check them out and let you know.

                If I understood the schematics correctly (btw i'm just a hobbyist), the 3A fuse provide current to power the inverter section, so blown fuse = no light, not even for half a second. am I right?


                Please notice that I never rebooted the pc in these four days before failing, just stand-by (yellow led) since i read the Davmax investigation about the BLT_ON issue, unfortunately the workaround is too complicated for my electronic skills to implement
                If the 3A fuse is blown but the transistors are fine then the monitor will turn on with a very quick blink on the LCD panel. I don't understand schematics either.

                Davmax's modification does not need to be put in, my two FP731 monitors are working fine without it. My electrical enginner buddy thinks that davmax's modification actually makes the design worse than its original configuration, and I heard that he said he has good reason for that claim.
                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

                • robd
                  New Member
                  • Apr 2008
                  • 2

                  #108
                  Re: Fix for Benq FP737s 17" (Q7T3)

                  I got one with the same problems, resoldered all trans and transformers and now i get a slow blink on the green LED any ideas is there a refurb board out there for this thing/

                  RD

                  Comment

                  • robd
                    New Member
                    • Apr 2008
                    • 2

                    #109
                    Re: Fix for Benq FP737s 17" (Q7T3)

                    Discard the top message and this is whats it still doing

                    I got one power led lights up for one second then off and wont come back on

                    RD

                    Comment

                    • agentsmithitaly
                      New Member
                      • Feb 2008
                      • 5

                      #110
                      Re: Fix for Benq FP737s 17" (Q7T3)

                      Originally posted by Newbie2
                      If the 3A fuse is blown but the transistors are fine then the monitor will turn on with a very quick blink on the LCD panel. I don't understand schematics either.

                      X Davmax:
                      1. Make sure that all the inverter transformer connections are resoldered
                      these connections seem fine to naked eye. I don't have a professional solder neither excellent soldering skills, i suppose i could worse the problem
                      2. Use a fast 3A fuse
                      Ok, I'll try to find it in a repair shop
                      3. Check the MOSFET in each circuit Q751 & Q743 (FU9024N) they should not read a short circuit.
                      I have ST D10PF06, I suppose they are equivalent. Could you provide a link to how to test with diode mode? I have to desolder them to test, right?


                      Thanks to everybody for all the suggestons


                      Hi Newbie,
                      I checked the 3A fuse and it isn't blown; I looked also the schematics and if the fuse was blown, there won't be current to the inverter, and no light.

                      However I tried to connect one lamp at a time and found that only one inverter it's working; the other one probably have a problem and triggers TL1451 protection mode.
                      But could be just another faulty transistor? the bad news is to get replacement parts from farnell or RS components would cost a lot (considering the price of new lcd monitor) and you aren't sure to fix it...
                      Last edited by agentsmithitaly; 05-17-2008, 10:29 AM.

                      Comment

                      • bassbindevil
                        Member
                        • Jun 2008
                        • 11

                        #111
                        Re: Fix for Benq FP737s 17" (Q7T3)

                        I suspect the failures are caused or at least aggravated by heat. On my FP731s, there aren't enough openings at the bottom of the metal shroud to allow cool air to enter.

                        I'm going to grab the Unibit and cut some bigger holes on the lower left and right of the shroud, next to the openings in the plastic outer cover, and along the bottom. That should improve air flow.

                        Only one of the four transistors was bad, but I've ordered 8 anyway, in case I can score another one of these.

                        Comment

                        • HOODLAM
                          Member
                          • Dec 2007
                          • 20

                          #112
                          Re: Fix for Benq FP737s 17" (Q7T3)

                          Hi Guys.
                          Just a followup after sevral months, my HP1955 is still on the go. I bought a spare set of 9024's which I will keep spare for just incase something happenes again.

                          One thing i found strange was the original fuse was a 3amp and the supply shop suggested i repalce with a 2amp cause it had to do with the voltage supply(220V), i installed the fuse about 7 months ago and still running!
                          Intel Core 2 Duo E6750 2.66Mhz 1333FSB
                          4 x 1Gb DDR800 Kingston
                          Geforce 8600GT 256Mb G/Card
                          1 x 320Gb Seagate SATAII
                          1 X 500Gb Seagate SATAII

                          Comment

                          • davmax
                            Badcaps Veteran
                            • Dec 2005
                            • 899

                            #113
                            Re: Fix for Benq FP737s 17" (Q7T3)

                            Originally posted by HOODLAM
                            Hi Guys.
                            Just a followup after sevral months, my HP1955 is still on the go. I bought a spare set of 9024's which I will keep spare for just incase something happenes again.

                            One thing i found strange was the original fuse was a 3amp and the supply shop suggested i repalce with a 2amp cause it had to do with the voltage supply(220V), i installed the fuse about 7 months ago and still running!
                            The shop guy gave you bad advice. The amp rating has nothing to do with the supply voltage of 220V. The fuse circuit operates on 15 volts DC irrespective of the supply. Lots of misinformation gets out from shop/counter guys.
                            Gigabyte EP45-DS3L Ultra Reliable (Power saver)
                            Intel E8400 (3000Mhz) Bios temps. 4096Mb 800Mhz DDR2 Corsair XMS2 4-4-4-12
                            160Gb WD SATAII Server grade
                            Nvidia 8500GT 256Mb
                            160Gb WD eSATAII Server grade for backup.
                            Samsung 18x DVD writer
                            Pioneer 16x DVD writer + 6x Dual layer
                            33 way card reader
                            Windows XP Pro SP3
                            Thermaltake Matrix case with 430W Silent Power
                            17" Benq FP737s LCD monitor
                            HP Officejet Pro K5300 with refillable tanks

                            Comment

                            • Cas123
                              New Member
                              • Jun 2008
                              • 2

                              #114
                              Re: Fix for Benq FP737s 17" (Q7T3)

                              Hi,
                              Just joined this forum. I have a Q7T3 that I inherited. Appears to have blown the 2 2SC5707 transistors as per this thread. Does anyone have any spare transistors they'd like to sell? Also the rear case mounting screws are missing. If anyone has a Q7t3 monitor they have given up on I would appreciate the screws.

                              Thanks, Ron...

                              Comment

                              • -LeonM-
                                New Member
                                • Jul 2008
                                • 2

                                #115
                                Re: Fix for Benq FP737s 17" (Q7T3)

                                Hello,

                                This is my first post on this forum, my name is Léon, and I am an electronics student from Holland.

                                I got a FP731, which has the same problem as the rest of these LCD's: the 2SC5707 transistors were blown, the LED was constantly flashing (screen kept rebooting). After opening the case, it quickly became clear that someone else already had a try at fixing it, the fuse was shorted (!) and there was some very messy soldering done on some of the transistors.

                                After replacing all four 2S5707's (I got them from Ebay), the screen worked for about 1 second, it displayed the Benq logo, and then white stripes appeared on the screen and it died. Once again one of the 5707's was blown.

                                So, after some investigation (I had not found these topics on this forum yet) I found out that:

                                1. It does not matter if the CCFL's are connected or not, the transistors wil blow anyway.
                                2. The transformers on my PCB are NOT shorted (desoldered every one of them and tested them with a signal generator and oscilloscope)
                                3. Just one of the two inverters keeps destroying transistors, the other one works just fine.
                                4. The two inverters seem to work parallel, because after removing the broken transistors form the inverter that kept failing, the screen actually worked!! As far as I could judge it had a normal brightness and the whole screen was lit (not just the upper/lower side).

                                After about 5 seconds, the backlight is turned off, probably because the single inverter gets overloaded, the image is still visible, the screen does not go on stand-by mode, it just turns the backlight off.


                                So, offcouse the question is: what could cause these transistors to die immediatly after the power is applied? I've checked all other transistors on the board, they all seem to be fine, the diodes are all good and there are no visible broken/shorted traces.

                                Does anyone have a suggestion where to look next?

                                Comment

                                • -LeonM-
                                  New Member
                                  • Jul 2008
                                  • 2

                                  #116
                                  Re: Fix for Benq FP737s 17" (Q7T3)

                                  update:

                                  Today I continued testen the board, to be 100% sure that the FET's were not faulty I swapped the FET's between the inverters, after powering up the inverter that always worked before still did. So the FET's, transformers and all others transistors besides the 5707's were actually fine.

                                  After desolering, checking and resoldering almost every component from the faulty inverter I still had no idea what the problem could be. I decided to give the monitor just one more chance to live before I would bring it to the scrapyard... I inserted the last pair of 5707's I had, powered it up and.... IT WORKS!

                                  I really don't have any idea what the problem was, it's now standing here on my desk next to my LG L203WT and it's working fine for over 2 hours now. Maybe I will build DavMax's circuit in someday, if it decides to die again

                                  For now, it's time to repair the next TFT: A Philips 170C...

                                  Comment

                                  • bassbindevil
                                    Member
                                    • Jun 2008
                                    • 11

                                    #117
                                    Re: Fix for Benq FP737s 17" (Q7T3)

                                    An update... I got the transistors and a fuse from a guy on eBay, stuck four new ones in along with the fuse, crossed my fingers, and plugged it in. It worked. Before buttoning it back up I checked one of the power supply caps, and it measured OK.

                                    I've been using the monitor for a while now, and it's still working. I'm starting to think these LCD monitors just might catch on... it's a lot smaller than my old 17" CRT, and even though it's not running at the native resolution, it is perfectly legible.

                                    Since getting this monitor, I also picked up a Viewsonic VX922... that one had bulging caps, which measured bad. I'm waiting for a DVI cable to put it into service, but it worked fine when I powered it up after changing the bad caps. I cut more ventilation holes in the shroud of that one too.

                                    Comment

                                    • gaztoo
                                      New Member
                                      • Jul 2008
                                      • 8

                                      #118
                                      Re: Fix for Benq FP737s 17" (Q7T3)

                                      G'Day Folks.

                                      Thanks to Davmax for initiating this thread and the fine work that he has done on the problem. I got one of these FP373's to repair and the problem was just the same as most others have found. One s/c 2SC5707 and o/c FP751 3A fuse.
                                      After sourcing the replacement parts all was well again. I did however, find many "dry" solder joints on the Inverter transformers and on other parts. I wonder if these could precipitate the problem.

                                      I am from Australia and if it will help, I found the following local sources for the 2SC5707s. They are rather special and no substitutes should be used.

                                      1 Wagner Electronics (Sydney) $1.75ea
                                      2 Farnell Electonics $2.12ea (currently out of stock)
                                      3 The Go Company (Brisbane) $7.95 ea (go figure)

                                      Comment

                                      • caddyroyalty
                                        New Member
                                        • Aug 2008
                                        • 1

                                        #119
                                        Re: Fix for Benq FP737s 17" (Q7T3)

                                        I just wanted to thank everybody here. I found a Benq FP731 in the recycle bin of a company and changed the 4 transistors and fuse and that took care of it. I'm using it now! I took pics and put them on Flickr, http://flickr.com/photos/caddyroyalt...7606746620272/

                                        Comment

                                        • electron
                                          New Member
                                          • Aug 2008
                                          • 2

                                          #120
                                          Re: Fix for Benq FP737s 17" (Q7T3)

                                          Hello,

                                          I would like some help to fix my LCD. I am not entirely sure, but it looks like the Q7T3, silver and black bezel. I dont have the bezel anymore. So I have a couple of questions and requests.

                                          1. If my screen is 17 inch, silver and black, does that narrow it down to a Q7T3, my screen looked like this

                                          Picture of my screen

                                          2. I see some different numbers and serial numbers, on the screen itself, internal bezel etc, but couldnt find any reference to them online. Can anyone help? Or no need to, since if my screen looks like the one above, it is a Q7T3?

                                          3. Most importantly and most appreciated, can anyone help me diagnoss, and then fix my screen?

                                          I can take pictures of the board as well.

                                          Whats broken: The screens backlights do not turn on. I really dont think the lamps are broken. I checked the LCD is still working, just no lights.

                                          Green power light turns to amber after a few seconds.

                                          voltmeter is getting a 1. volt reading from the power outputs to the lamps.

                                          Thanks so much, if you would really like to help please email me!

                                          Comment

                                          Related Topics

                                          Collapse

                                          • x_orange90_x
                                            Vizio E55-E1 bad backlights or bad inverter?
                                            by x_orange90_x
                                            I just got this tv today and it appeared to have no backlight on. After taking off the rear cover and checking again in the dark I can see that MAYBE one quadrant is lit.. But still it's quite dim. I was going to check the LEDs with my tester, and I found LED 1 and LED 2 + pins on the wire from the inverter, but I couldn't identify a ground. Nonetheless I tried using a mounting screw on the inverter board and also the chassis as ground but regardless my tester reads 300 which is what it reads when there is no voltage draw.

                                            I don't know how exactly to test the inverter itself. Is it...
                                            01-29-2025, 09:24 PM
                                          • Gentian
                                            APSINT3636VR 3600W APS INT Series 36V DC 230V AC Inverter/Charger schematic
                                            by Gentian
                                            I have a tripp-lite aspint 3636vr inverter charger which blow some of mosfet transistors. I replaced them repaired also the driver circuit and tested but the mosfets burn again.

                                            It work very well as inverter and also as charger if I let the rear switch in auto mode (inverter) and charger only(charging) but in auto when I connect the feed line 220V AC first time it pass ok to line and start charging the batteries but when I remove the feed line it pass to inverter mode and if I do it again the second time when passing from charging to inverter the Main transformer start making a...
                                            03-06-2023, 07:07 AM
                                          • valvashon
                                            Insignia NS-LCD19-09 (PS OK, Inverter problem?)
                                            by valvashon
                                            For some reason I'm just not going to let this 19" TV defeat me. I guess because I have a schematic to work from I feel like I'm oh so close.

                                            History- while adding a turn-on circuit I let a small screw roll under the power board. Worked through all of that circuitry, probably replacing a MOSFET and PWM controller that were not bad but I was following the service manual. Finally figured out that the power supply is in working order when the inverter section (for the backlights) is disconnected. When the +12 supply to the inverter is disconnected the +12 and +5 will come up...
                                            01-04-2024, 01:44 PM
                                          • eccerr0r
                                            A modified sine wave inverter + a grid tie inverter?
                                            by eccerr0r
                                            If I had a solar fed grid tie inverter (GTI), a modified sine wave inverter, and a power outage occurred, what would happen if you disconnected mains, backfed the modified sinewave inverter (MSI) into house power, and hooked up the GTI to the output of the MSI, would it work?

                                            Next thing is trying to charge the batteries using solar power, but that's another issue ...
                                            08-31-2023, 09:14 PM
                                          • caseyjay_48
                                            Sony KDL-46BX450 Inverter Troubleshoot Logic
                                            by caseyjay_48
                                            I am currently on a troubleshoot of 46” Sony KDL-46BX450 tv. I came back from Washington to Texas on medical emergency and had to leave all my tools up there. All I have is a couple of screwdrivers and a dvm. I wish to ask the community a troubleshooting question. Please forgive stupid questions as meds I am taking produce brain fog.
                                            I have well maintained Sony KDL-46BX450. It went black one day. After turn-on, I get solid green light and Sony logo in screen center for about 1-2 seconds, then black. No blinking LEDs, no hissing. Flashlight test shows screen characters dimly viewable,...
                                            09-23-2022, 08:08 PM
                                          • Loading...
                                          • No more items.
                                          Working...