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    BenQ FP91G+ wont stay on

    Hello crowd!

    I have come for suggestions about a BenQ FP91G+ LCD.

    I know only enough about electrical components (board level) to be dangerous however Im a wizard at using them. I do learn and understand fast With that said i dont know where to begin and would appreciate a nudge in the right direction.

    when i plug the LCD in and press the power button, the power LED comes on green then turns off right away

    The inverted MAY be fried, but at this point i believe that is irrelevent since the power LED wont even stay on.

    i have a few ideas but would like to throw those out there:
    -Do LCDs use same voltages as regular computer? 3.3, 5, 12?
    My thinking is that if they do, use a bench power supply to test the LCD, if that works then i know the LCD power supply is bad. For some reason i dont think its going to be that cut and dry.......
    -short?
    -something fried like a fuse?


    I have a multimeter and acceptance that i will get shocked again one day (good thing usa uses 110v)

    #2
    Re: BenQ FP91G+ wont stay on

    Please post good clear pictures of all the board using advanced function for file attachment.
    If the inverter has shorted circuits, it will cause the main power supply to shutdown to protect itself.
    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


      #3
      Re: BenQ FP91G+ wont stay on

      Thought you were a noob when there are no pics to accompany your story.

      Here is a thread that sets out the main problems with this monitor
      (no pics there either!)
      https://www.badcaps.net/forum/showth...ighlight=FP91G

      The inverted MAY be fried, but at this point i believe that is irrelevent since the power LED wont even stay on. - Correct

      i have a few ideas but would like to throw those out there:
      -Do LCDs use same voltages as regular computer? 3.3, 5, 12? -Quite often
      My thinking is that if they do, use a bench power supply to test the LCD, if that works then i know the LCD power supply is bad. Yes but as you say
      For some reason i dont think its going to be that cut and dry.......
      There was a post recently telling how to do this - I will find it and add as an edit.
      -short? Possibly
      -something fried like a fuse? - possibly For some reason i dont think its going to be that cut and dry.......

      Did you have the board and it stopped working - found it on the pavement?

      We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

      Please do not post inline and offsite as they slow down the loading of pages.

      Examples of what is needed
      https://www.badcaps.net/forum/attach...1&d=1290283049

      https://www.badcaps.net/forum/attach...7&d=1280167246

      When you open it up you will probably find the voltages printed near the connectors.


      EDIT https://www.badcaps.net/forum/showpo...9&postcount=15
      Last edited by selldoor; 06-11-2012, 02:54 PM. Reason: add link
      Please upload pictures using attachment function when ask for help on the repair
      http://www.badcaps.net/forum/showthread.php?t=39740

      Comment


        #4
        Re: BenQ FP91G+ wont stay on

        Great, thanks. I will get pictures sometime today

        apparently my google foo needs some rework, i tried searching (for similar posts) befor i poseted but came up dry (site:*.badcaps.net)

        As for this monitor, I help a a few people with their computers, one of those people called me about this one, we had already replaced it and they just wanted to trash it. This one was working friday, came back monday and it stops working. my goal is fix it and replace an old crt i have on the bench.

        Comment


          #5
          Re: BenQ FP91G+ wont stay on

          The first thing to do is always to open the unit and examine it. The shut down is consistent with the problem my FP91G had, bad caps. They were obviously (visually easy to see that they were) vented and swapping in good caps solved the problem.

          Definitely not a fuse, it wouldn't come on at all if that were the problem, would seem 100% dead. If you see vented caps I wouldn't even bother with any other testing before replacing them and trying to power it on.

          Comment


            #6
            Re: BenQ FP91G+ wont stay on

            Originally posted by 999999999 View Post
            The first thing to do is always to open the unit and examine it. The shut down is consistent with the problem my FP91G had, bad caps. They were obviously (visually easy to see that they were) vented and swapping in good caps solved the problem.

            Definitely not a fuse, it wouldn't come on at all if that were the problem, would seem 100% dead. If you see vented caps I wouldn't even bother with any other testing before replacing them and trying to power it on.

            I have pics, my camera is not the best quality...

            After looking at it, right away i see 8 bad craps (bulging) on the power supply, one of them oozing.

            I will take your suggestion 9x9, replace those and go from there. Im almost certain it will fix this problem.


            2x Jamicon?10v 1000uf
            6x elite 35v 470uf

            Is there a rule of thumb for capacitors replacement can go by as i dont have exact ones? I have various ones laying around but different voltages and capacitance.
            edit: i only have some (new) rubicon 6.3v 2200 uf, i suppose i cant use those. rest are ones i pulled off other parts.
            Attached Files
            Last edited by mattch; 06-13-2012, 08:41 AM. Reason: edit

            Comment


              #7
              Re: BenQ FP91G+ wont stay on

              Hi - no you cant use the 6.3v ones - here is a guide
              http://www.niccomp.com/help/capsubguide.asp

              Sometimes it is good to increase the voltage by one notch but the uf value should be maintained unless you know what your doing.

              Using old ones - unless you can test with an esr meter may not be a good idea if bad they could cause knock on damage to components more expensive and more difficult to replace.

              Some members would recommend replacing all capacitors of same makes that have gone.
              Retiredcaps has an insert he uses s - I will add if I can find it.
              EDIT
              https://www.badcaps.net/forum/showpo...84&postcount=3
              Last edited by selldoor; 06-13-2012, 09:27 AM.
              Please upload pictures using attachment function when ask for help on the repair
              http://www.badcaps.net/forum/showthread.php?t=39740

              Comment


                #8
                Re: BenQ FP91G+ wont stay on

                Thanks, that website is great.

                as a matter of fact all of the elite and jamicon ones are bulged (hard to see from pic) so all will replaced. But that makes perfect sense as to why i would replace all of the same ones even if they otherwise look ok.

                Being as impatient as i am, i would like to run out and pick up replacments today.
                Is radioshack a bad idea? seems they are all NTE brand
                Last edited by mattch; 06-13-2012, 09:48 AM.

                Comment


                  #9
                  Re: BenQ FP91G+ wont stay on

                  Not a great idea - I am not saying they wont work but you may have to replace in a few weeks time - again if they go they can take other components with them.
                  They are just not good for this application, obviously its your choice but not recommended.
                  Please upload pictures using attachment function when ask for help on the repair
                  http://www.badcaps.net/forum/showthread.php?t=39740

                  Comment


                    #10
                    Re: BenQ FP91G+ wont stay on

                    Avoid radio shack caps, every now and then they have sold some Nichicons (PW or PM series, I forget which) in the assorted cap packs that were close to what you'd want (105C temp, very low ESR) in type but not the right values and sizes.

                    For your needs Digikey is the best bet. With a small order like this (under 8 oz.) they can ship it USPS for around $2 and it'll arrive in 2 or 3 days (average).

                    Comment


                      #11
                      Re: BenQ FP91G+ wont stay on

                      got it. i will order those, i think ill checkout the badcaps store since i have to wait either way.

                      many thanks for all the suggestions, once i get the caps i will post results. Then probably open a few more bad lcds i have laying around =D.

                      Comment


                        #12
                        Re: BenQ FP91G+ wont stay on

                        Originally posted by mattch View Post
                        Being as impatient as i am, i would like to run out and pick up replacments today.
                        Is radioshack a bad idea? seems they are all NTE brand
                        RadioShack is unlikely to stock or sell low ESR caps which are required for the power supply (SMPS application). They are likely to carry general purpose caps which have different characteristics than low ESR caps and not suitable for SMPS application.
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