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BenQ FP71e Q7C4 2 seconds to dead

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    #1

    BenQ FP71e Q7C4 2 seconds to dead

    Working on a BenQ FP71e. Recapped, but still 2 seconds to dead.
    That is, power led comes on for 2 secs, then turns off.

    I figure something is killing the power supply, then I notice its the all too familiar C5707 transistors, and sure enough a couple are shorted.

    Looks like this model uses D10PF FETs instead of the FU9024N.
    Some sellers on Ebay claim they're interchangable. The one that isn't shorted reads very similar to an FU9024N on my Peak tester.
    I have some FU9024s on-hand so am tempted to use them.

    Looking at the Datasheets I'm confused. I don't know jack about FETs so maybe I'm just being stupid..

    THe D10PF says Vds 60v Vdgr 60v Vgs +/- 20v Id 10A

    The FU902N says Vds -55v Id -11A etc. What's up there? They're both P-Channel what's with the negative voltage/current ratings?
    Attached Files
    36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....
    Tags: None
    #2
    Re: BenQ FP71e Q7C4 2 seconds to dead

    I have a BenQ which uses the D10PF. One promptly went snap, crackle, pop after I'd (badly) repaired the rest of it. Man those boards are delicate.
    Had them on back order since October 2010, should be here April 2011!

    Comment

      #3
      Re: BenQ FP71e Q7C4 2 seconds to dead

      Hi on the reverse side of the board (ringed in yellow on the pic 0

      Is there another under there FQU11P06 should be the number on that part if so that can be replaced by a FU9024

      Looks to be a burn mark worth a check not sure about the others tho
      Attached Files

      Comment

        #4
        Re: BenQ FP71e Q7C4 2 seconds to dead

        You're right it does look like that part of the board has been hot.
        I'll check that component. It's labelled as IC701 I'll have to see if I can get a part number off of it.

        Does anyone have comments on my question about the Datasheet info?
        36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

        Comment

          #5
          Re: BenQ FP71e Q7C4 2 seconds to dead

          The only marking left on this component is F2 in a circle at the top of the device.
          It looks like a voltage regulator.
          Attached Files
          36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

          Comment

            #6
            Re: BenQ FP71e Q7C4 2 seconds to dead

            Well I got impatient and used FU9024Ns and it works.
            Will re-assemble and leave on test tomorrow.

            Man that's a crappy quality PCB. I lifted one trace while desoldering (not like me)
            And after I put in one of the 5707s I went to bend it away from a cap that it was touching, and broke 2 traces. fun.
            Last edited by smason; 02-21-2011, 09:57 PM.
            36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

            Comment

              #7
              Re: BenQ FP71e Q7C4 2 seconds to dead

              I had the same issue with another Benq after changing caps and transistors and redoing all solder joints still had the 2 sec to black and it ended up being that component .
              I may have service manual for this one and will try to check to see what its supposed to be

              Comment

                #8
                Re: BenQ FP71e Q7C4 2 seconds to dead

                Originally posted by smason View Post
                .

                Man that's a crappy quality PCB. I lifted one trace while desoldering (not like me)
                And after I put in one of the 5707s I went to bend it away from a cap that it was touching, and broke 2 traces. fun.
                Every once and a wile I will damage a trace also; usually it will be a capacitor on a board in a Samsung.
                If you ever damage the pad and you have trouble finding out where it goes to. With a very small diameter sewing needle I probe sideways between the layers into the damaged hole, and with an ohmmeter I am able to trace where it goes, and do the repair.
                Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

                Comment

                  #9
                  Re: BenQ FP71e Q7C4 2 seconds to dead

                  If it is IC701 then according to the sheet i have you are right 3.3v reg
                  Attached Files

                  Comment

                    #10
                    Re: BenQ FP71e Q7C4 2 seconds to dead

                    Cool, thanks for the schematics!!!!

                    36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                    Comment

                      #11
                      Re: BenQ FP71e Q7C4 2 seconds to dead

                      Hello smason, can you tell me how to repair that monitor? What thing I need to change there?

                      Comment

                        #12
                        Re: BenQ FP71e Q7C4 2 seconds to dead

                        Thanks for the circuit diagram and info. I have just managed to fix my FP737s after its 470uF 35V caps had failed.

                        Sadly it still did not work after replacing the capacitors, as there was no backlight. Although the circuits for the FP71e were not exactly the same, they were close enough and I was able to ascertain that the fuse (PF801 on the Q7C4) had blown. Fortunately, no semiconductors had been damaged and it's all working again.

                        Comment

                          #13
                          Re: BenQ FP71e Q7C4 2 seconds to dead

                          Originally posted by andyfras View Post
                          Thanks for the circuit diagram and info. I have just managed to fix my FP737s after its 470uF 35V caps had failed.

                          Sadly it still did not work after replacing the capacitors, as there was no backlight. Although the circuits for the FP71e were not exactly the same, they were close enough and I was able to ascertain that the fuse (PF801 on the Q7C4) had blown. Fortunately, no semiconductors had been damaged and it's all working again.
                          Well done.

                          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

                            #14
                            Re: BenQ FP71e Q7C4 2 seconds to dead

                            Originally posted by andyfras View Post
                            Although the circuits for the FP71e were not exactly the same, they were close enough and I was able to ascertain that the fuse (PF801 on the Q7C4) had blown.
                            You MUST resolder all the inverter transformer pins. These Benq models have poor solder joints and will cause the picofuse to blow again if you don't resolder them.

                            Also resolder the square grey caps by those transformers.
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                            Comment

                              #15
                              Re: BenQ FP71e Q7C4 2 seconds to dead

                              Originally posted by retiredcaps View Post
                              You MUST resolder all the inverter transformer pins. These Benq models have poor solder joints and will cause the picofuse to blow again if you don't resolder them.

                              Also resolder the square grey caps by those transformers.
                              I did a visual check of the joints before I put it back together. If (when) the fuse blows again, I'll resolder the joints as you suggest. Thank you for the tip.

                              I assumed, perhaps wrongly, that the fuse had blown as a result of excessive ripple on the supply due to failed capacitors.

                              Comment

                                #16
                                Re: BenQ FP71e Q7C4 2 seconds to dead

                                Originally posted by andyfras View Post
                                If (when) the fuse blows again, I'll resolder the joints as you suggest.
                                Well that didn't last long!

                                It failed again, but this time it took out one of the C5707s. I have ordered a repair kit from eBay - 4 x C5707, 2 x FU9024N, 1x 3A 125V fuse for £3.85 delivered.

                                I have gone over all the solder joints on the transformers and associated components.

                                Hopefully the fix will last a bit longer this time.

                                Comment

                                  #17
                                  Re: BenQ FP71e Q7C4 2 seconds to dead

                                  Originally posted by andyfras View Post
                                  Well that didn't last long!
                                  I did warn you!
                                  --- begin sig file ---

                                  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

                                    #18
                                    Re: BenQ FP71e Q7C4 2 seconds to dead

                                    Repaired again.

                                    Hopefully it'll last a bit longer this time.

                                    Comment

                                      #19
                                      Re: BenQ FP71e Q7C4 2 seconds to dead

                                      Anybody has this one still around? I got the infamous rotten main cap, replaced it together with fuse but in my endless stupidity haven't checked for any other problem. Most likely the single transistor was shorted, now after pluging in also the 8pin IC is blown and some SMD resistors (yet fuse is intact).

                                      I think good start would be with the IC, anybody knows what is is? I am unable to indetify it on the pictures. I'll have a look if it is worth looking after as it may be the most uncommon component in the display.
                                      Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

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                                      Hardware Insights - power supply reviews and more!

                                      Comment

                                        #20
                                        Re: BenQ FP71e Q7C4 2 seconds to dead

                                        If you mean the 8 pin through-hole DIP IC on the top pf the power supply pcb, on mine it was a 1200AP40 PWM controller. Should be easy to find. Maybe not locally for you.

                                        http://www.datasheetdir.com/1200AP40+PWM-Controllers

                                        Here's one for 0.99 in the UK
                                        http://www.logictoyz.com/electronic-...ontroller.html
                                        Last edited by smason; 04-23-2013, 10:51 AM.
                                        36 Monitors, 3 TVs, 4 Laptops, 1 motherboard, 1 Printer, 1 iMac, 2 hard drive docks and one IP Phone repaired so far....

                                        Comment

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