Acronym U: what for?

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  • Behemot
    Badcaps Legend
    • Dec 2009
    • 4845
    • CZ

    #1

    Acronym U: what for?

    As the title says, got SMD components marked as, say, U12, U23 and so. What is that?
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  • ratdude747
    Black Sheep
    • Nov 2008
    • 17136
    • USA

    #2
    Re: Acronym U: what for?

    Moved out of FAQ. Seriously, you have 1000+ posts... you should know better...

    ---

    Parts marked with a U are usually ICs... Sometimes it can include transistors too (but they usually are marked with a Q). Beyond that, you'd have to look at the chip itself or a service manual schematic.
    sigpic

    (Insert witty quote here)

    Comment

    • kikkoman
      Badcaps Veteran
      • Jul 2007
      • 691

      #3
      Re: Acronym U: what for?

      On the silkscreen or on the parts themselves?
      If on the silkscreen, it usually means it's some sort of IC (anything up from a simple voltage regulator, so anything that's not a discrete part.).

      If on the parts, that is much trickier. What's the footprint and silkscreen marking?
      "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin slitting throats." - H.L. Mencken

      Comment

      • martin114
        New Member
        • Feb 2013
        • 1
        • uk

        #4
        Re: Acronym U: what for?

        This might help...
        SMD Codes U1, U1**, U12, U13, U16, U17
        http://www.s-manuals.com/smd/u1
        http://www.s-manuals.com/smd/u2
        Cheers,
        Martin.

        Comment

        • Behemot
          Badcaps Legend
          • Dec 2009
          • 4845
          • CZ

          #5
          Re: Acronym U: what for?

          Here it is. Supposedly the lady owner somehow managed to push the plastic crap inside the USB onto the board and tear off couple SMD components. But it seems the U, whatever it is, was not even present before?

          ratdude747: I am not sure whether I'll ever understand the schematics of this part of the forums
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          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #6
            Re: Acronym U: what for?

            Are you talking about IC U25 the 8-pin IC?
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            • Behemot
              Badcaps Legend
              • Dec 2009
              • 4845
              • CZ

              #7
              Re: Acronym U: what for?

              Nope, U39, there is SMD cap and inductor teared off. Eh, do you think it's the big GST5009 chip? Don't I see a forest because of the trees?
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              • kc8adu
                Super Moderator
                • Nov 2003
                • 8832
                • U.S.A!

                #8
                Re: Acronym U: what for?

                l58=l66
                c740=c821
                just look off the port to the left.

                Comment

                • Behemot
                  Badcaps Legend
                  • Dec 2009
                  • 4845
                  • CZ

                  #9
                  Re: Acronym U: what for?

                  Yeah for sure, I haven't been initially sure about what's the U39, but now I see it clearly that the positions I though were for two components are actually for the single inductor, and U39 is most likely the big chip.
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                  • budm
                    Badcaps Legend
                    • Feb 2010
                    • 40746
                    • USA

                    #10
                    Re: Acronym U: what for?

                    C740/C821 are more likely the filter caps for the +5V for pin 1 of the USB.
                    The two small traces (connected to the Diff-mode inductor) are more likely to be for the + and - pins of the USB.
                    You can test out the connections of the USB pins to those missing components. You can also put the jumper on the missing Inductor (for noise filter?) to test out if the USB port will function.
                    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

                    • redwire
                      Badcaps Legend
                      • Dec 2010
                      • 3906
                      • Canada

                      #11
                      Re: Acronym U: what for?

                      Since there's two USB ports, I see that L66 is the same as L58 (which is busted off) a common-mode (dual, 4-pads) choke. C740 is also busted off but the same as C821 for EMI on the USB connector shield.
                      In a pinch, I would just jumper the two USB data traces on L58 and that should get the port working at least. C740 is usually 10nF and not that important because it's EMI related.
                      U39 on the silkscreen refers to the part below it, the GST5009 Ethernet transformer.

                      Comment

                      • redwire
                        Badcaps Legend
                        • Dec 2010
                        • 3906
                        • Canada

                        #12
                        Re: Acronym U: what for?

                        Second look and C740 as Budm says, might be for 5V power (like 10-100uF) but it's weird the cap is mirror-image position to C821.

                        Comment

                        • lti
                          Badcaps Legend
                          • May 2011
                          • 2547
                          • United States

                          #13
                          Re: Acronym U: what for?

                          It looks like there is a tiny cap above C740 that has also been removed.

                          Comment

                          • budm
                            Badcaps Legend
                            • Feb 2010
                            • 40746
                            • USA

                            #14
                            Re: Acronym U: what for?

                            That is more likely to be .01UF cap in parallel with the larger value missing cap (10uf or more as redwire suggested).
                            By the way, typo on my part, it is common mode choke for common mode noise rejection as redwire had indicated. Just bypass it for now.
                            Last edited by budm; 04-25-2013, 10:19 PM.
                            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

                            • Behemot
                              Badcaps Legend
                              • Dec 2009
                              • 4845
                              • CZ

                              #15
                              Re: Acronym U: what for?

                              I may actually have few of the missing componens.as for the inductor, I guess two in parallel may do the trick? If I won't find any, than I'll just use some wire
                              Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

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                              • budm
                                Badcaps Legend
                                • Feb 2010
                                • 40746
                                • USA

                                #16
                                Re: Acronym U: what for?

                                The inductor windings are not connected in parallel, the windings are on the same core. just look up commomn mode choke to see how it's done, I would just bypass it for now to test, if the USB cable is short and not close to electrical noise then you mat get by without it.
                                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

                                • Behemot
                                  Badcaps Legend
                                  • Dec 2009
                                  • 4845
                                  • CZ

                                  #17
                                  Re: Acronym U: what for?

                                  Ah yeah, common mode, I see. Two differential will have to do
                                  Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

                                  Exclusive caps, meters and more!
                                  Hardware Insights - power supply reviews and more!

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