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    #1

    Optiquest Q7 Power Supply

    I've got an Optiquest Q7 LCD that stays on for about 2 seconds and then the display drops out. I've disassembled the monitor and found several bulging caps on the power supply board. (circled in blue in attatched picture)

    These consist of the following:

    3x CapXon 470uF 25V "KF 105^o C C610 VENT"
    1x CapXon 330uF 25V "KF 105^0 C C612 VENT"

    The big guy (outlined in red) is a CapXon 400v 100uF, reading at well below 100uF, more like .1 nF.

    My main question is really just to get a recommendation for ordering parts for this repair.

    Any help would be appreciated.
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    #2
    Re: Optiquest Q7 Power Supply

    The first post didn't seem to attach the image, so here it is.

    Comment

      #3
      Re: Optiquest Q7 Power Supply

      Originally posted by TX-ZoSo View Post
      The big guy (outlined in red) is a CapXon 400v 100uF, reading at well below 100uF, more like .1 nF.

      My main question is really just to get a recommendation for ordering parts for this repair.
      The forum members here often say that the big cap rarely, but not never, fails. Here is a good example of a big cap that has failed measuring well below its uF.

      There is no picture, but if you follow PlainBill's instructions below, you can order Panasonic FM caps at digikey.com

      https://www.badcaps.net/forum/showpo...33&postcount=2
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        #4
        Re: Optiquest Q7 Power Supply

        Originally posted by TX-ZoSo View Post
        The first post didn't seem to attach the image, so here it is.
        Please don't post images inline or use offsite hosting. Use the manage attachments. If your pic is 2000x2000 and less than 2MB, it should load fine here using manage attachments.

        The advanced edit button will let you correct your inline post.

        Otherwise, it is clear excellent focused picture.
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          #5
          Re: Optiquest Q7 Power Supply

          Originally posted by TX-ZoSo View Post
          I've disassembled the monitor and found several bulging caps on the power supply board.
          Replace C320 as well too. It plays an important role in the startup process. Since every other capacitor on the board as failed, it would not be a stretch to think that C320 is near its useful life.

          Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad.
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            #6
            Re: Optiquest Q7 Power Supply

            Excellent. Thanks for the prompt response.

            Comment

              #7
              Re: Optiquest Q7 Power Supply

              Originally posted by retiredcaps View Post
              The forum members here often say that the big cap rarely, but not never, fails. Here is a good example of a big cap that has failed measuring well below its uF.
              I've never had a Capxon primary fail on me, but I would replace Taicon primaries on sight.
              "We have offered them (the Arabs) a sensible way for so many years. But no, they wanted to fight. Fine! We gave them technology, the latest, the kind even Vietnam didn't have. They had double superiority in tanks and aircraft, triple in artillery, and in air defense and anti-tank weapons they had absolute supremacy. And what? Once again they were beaten. Once again they scrammed [sic]. Once again they screamed for us to come save them. Sadat woke me up in the middle of the night twice over the phone, 'Save me!' He demanded to send Soviet troops, and immediately! No! We are not going to fight for them."

              -Leonid Brezhnev (On the Yom Kippur War)

              Comment

                #8
                Re: Optiquest Q7 Power Supply

                What's with the large 470 ohm 5W Xicon resistor acoss the primary cap?

                Comment

                  #9
                  Re: Optiquest Q7 Power Supply

                  I used it to make sure that the cap was discharged. Forgot to remove it before I snapped the pic.

                  Comment

                    #10
                    Re: Optiquest Q7 Power Supply

                    Originally posted by TX-ZoSo View Post
                    I used it to make sure that the cap was discharged.
                    I did a test on one of my monitors and it doesn't apply to all monitors, but I hooked up my multimeter to the big cap and measured 160ish V DC.

                    I powered off and unplugged the power cord. I watched the multimeter and saw the big cap discharge over about a 1 minute period.
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                      #11
                      Re: Optiquest Q7 Power Supply

                      Originally posted by retiredcaps View Post
                      I powered off and unplugged the power cord. I watched the multimeter and saw the big cap discharge over about a 1 minute period.
                      Ah, I'm used to working on tube amps. The filter caps in those must have gotten me paranoid.

                      Good to know that these discharge that quickly though.

                      Comment

                        #12
                        Re: Optiquest Q7 Power Supply

                        Originally posted by TX-ZoSo View Post
                        Ah, I'm used to working on tube amps. The filter caps in those must have gotten me paranoid.

                        Good to know that these discharge that quickly though.
                        There is a high value resistor (100K) that provides startup power to the SMPS controller that will discharge the large cap fairly quickly. However, that resistor going open is one (rare) failure mode for the power supply.

                        The moral is: Better safe than sorry.

                        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

                          #13
                          Re: Optiquest Q7 Power Supply

                          Originally posted by PlainBill View Post
                          The moral is: Better safe than sorry.
                          Agreed.

                          In fact, I switched the way I measure the main filter cap by using aligator clips on my multimeter. I clip everything in, double check all my connections/polarity, and then hit the power bar switch. That is how I did the above test.
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                            #14
                            Re: Optiquest Q7 Power Supply

                            Originally posted by PlainBill View Post
                            There is a high value resistor (100K) that provides startup power to the SMPS controller that will discharge the large cap fairly quickly. However, that resistor going open is one (rare) failure mode for the power supply.

                            The moral is: Better safe than sorry.

                            PlainBill

                            I agree with PlainBill. I always first check the voltage across the main cap before I do anything else. This rule applies to everything run off of line voltage. SAFETY FIRST!

                            Comment

                              #15
                              Re: Optiquest Q7 Power Supply

                              Originally posted by jetadm123 View Post
                              SAFETY FIRST!
                              Can't agree more, been zapped last month by a 17" LG Flatron (crt) that had an open bleeder resistor on the primary cap. Not fun.
                              Originally posted by PeteS in CA
                              Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
                              A working TV? How boring!

                              Comment

                                #16
                                Re: Optiquest Q7 Power Supply

                                Hi all, this is my first post. I fixed an LCD monitor about a month ago by replacing a cap. Yesterday, I tried fixing my Optiquest Q7 monitor by fixing 4 bad caps. Problem is, when I had the new caps soldered in and went to power on the monitor nothing ever happened. I was checking over other parts and found that the L660 was loose. I removed it and am now looking to replace.

                                Go figure, I see this post which is almost exactly related to the power board I'm correcting!!

                                The image previously shown in this thread is the same as my power board.

                                The thing is, what IS in the L660? Its a tiny half a centimeter black rod that had copper rapped around it. I need to get a new one but I just can't locate what it is.

                                Can anybody help?

                                Also, on the Q7, does anybody have the CN1, CN2, CN3, CN4 connector color code for reconnecting the display to the power board?

                                Thanks in advance!!

                                Comment

                                  #17
                                  Re: Optiquest Q7 Power Supply

                                  Originally posted by BlexClex View Post
                                  Hi all, this is my first post. I fixed an LCD monitor about a month ago by replacing a cap. Yesterday, I tried fixing my Optiquest Q7 monitor by fixing 4 bad caps. Problem is, when I had the new caps soldered in and went to power on the monitor nothing ever happened. I was checking over other parts and found that the L660 was loose. I removed it and am now looking to replace.

                                  Go figure, I see this post which is almost exactly related to the power board I'm correcting!!

                                  The image previously shown in this thread is the same as my power board.

                                  The thing is, what IS in the L660? Its a tiny half a centimeter black rod that had copper rapped around it. I need to get a new one but I just can't locate what it is.


                                  Can anybody help?

                                  Also, on the Q7, does anybody have the CN1, CN2, CN3, CN4 connector color code for reconnecting the display to the power board?

                                  Thanks in advance!!

                                  If L660 was loose because of a bad solder joint and if there's no physical damage, just go ahead and solder it back in. The black rod is ferrite.
                                  Last edited by jetadm123; 12-08-2010, 04:29 PM.

                                  Comment

                                    #18
                                    Re: Optiquest Q7 Power Supply

                                    Thanks, but I ripped the copper off of the black rod. I'm assuming I just place the black rod back on, wrap some of the left over copper around it and put it back in? Thank you again!

                                    Comment

                                      #19
                                      Re: Optiquest Q7 Power Supply

                                      Originally posted by BlexClex View Post
                                      Thanks, but I ripped the copper off of the black rod. I'm assuming I just place the black rod back on, wrap some of the left over copper around it and put it back in? Thank you again!
                                      L indicates inductor. It is a number of turns of wire, often with an iron or ferrite core. The core material, number of turns, and to a certain extent the gauge of wire are important. When you say 'left over copper' it gives the impression that some of the wire is missing. Is that correct?

                                      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

                                        #20
                                        Re: Optiquest Q7 Power Supply

                                        Yes, I pulled the iron or ferrite core out and pulled the wiring off of it too. There is one piece of wire left in one of the two L660 slots and it's about 3 inches long currently.

                                        I figured I could easily buy a replacement one but it's turned out to be a lot more complex of a replacement than I thought.

                                        Thanks

                                        Comment

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