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New tool to find short capacitors on motherboards : shorty with display

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    #81
    Re: New tool to find short capacitors on motherboards : shorty with display

    Originally posted by kripton2035 View Post
    I received the pcb some times ago. but there is a failure I did not find until now.
    I made some changes in the schematic, using a constant current source for better repetability,
    well I'm still investing. the voltage regulator is giving 2.4V instead of 5V
    ... and it does not seems to be a short circuit !
    Some more info about?
    I mean about voltage regulator.

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      #82
      Re: New tool to find short capacitors on motherboards : shorty with display

      do you mean your not getting enough current from the one on the arduino?
      that doesnt surprise me really.
      you probably need to use a 1A linear regulator and some tantalum caps

      Comment


        #83
        Re: New tool to find short capacitors on motherboards : shorty with display

        I added a voltage regulator 1755S to bypass the one inside the arduino. just thinking there would be a better regulation than the 1117. I also added a constant current source with the pnp transistor, to have better accuracy and better reproductibility of the measures.
        now I'm debugging this new schematic, it's almost working, but as a reminder it is a hobby project, and I have been very busy these last months.

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          #84
          Re: New tool to find short capacitors on motherboards : shorty with display

          I was more about

          I'm still investing. the voltage regulator is giving 2.4V instead of 5V
          As I see 1755S is limited to 300mA
          Aprox 60mA via Q1 and resistors, 240mA for Arduino, oled and others.

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            #85
            Re: New tool to find short capacitors on motherboards : shorty with display

            I checked on a lab power supply, the whole device is now using 50-60mA.
            the current constant source now is using 30mA.

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              #86
              Re: New tool to find short capacitors on motherboards : shorty with display

              Some schematic will help a lot.
              Where did you get 2.4V instead of 5V with voltage regulator?
              Also
              Voltage drop C-E on BC557 at 100 mA is in datasheet 0.65V
              5V -Vdrop on BC557 = 4.35V
              4.35V on 82 + 2 +1 ohms is around 0.051A that is 51mA but since it may be pulsing lab power supply will show some intermediate value.

              I'm not so familiar with Arduino but in source code seems like you defined TRANSISTOR and BUTTON both to pin 3

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                #87
                Re: New tool to find short capacitors on motherboards : shorty with display

                I'm not so familiar with Arduino but in source code seems like you defined TRANSISTOR and BUTTON both to pin 3
                transistor is on an analog pin 3 A3, and button on a digital pin 3 D3
                they are not the same pin.
                anyway, the transistor is always on, and has been removed from the source code when I use the constant current source.

                Comment


                  #88
                  Re: New tool to find short capacitors on motherboards : shorty with display

                  this is the actual state of the schematic of the shorty-with-display input stage.
                  Attached Files

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                    #89
                    Re: New tool to find short capacitors on motherboards : shorty with display

                    Are both 3 but must be something to differentiate.
                    For digital pin you can define simple with number only but for analog inputs you need to specify is analog one by using A prefix.

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                      #90
                      Re: New tool to find short capacitors on motherboards : shorty with display

                      Hi Kripton
                      Do you have any up to date news regarding the PCB?
                      Follow me on YouTube
                      ------------------
                      Learn Electronics Repair
                      https://www.youtube.com/channel/UCFX...R8UZ2vg/videos

                      Comment


                        #91
                        Re: New tool to find short capacitors on motherboards : shorty with display

                        Originally posted by dicky96 View Post
                        Do you have any up to date news regarding the PCB?
                        He has been busy with work. I have considered building one from the schematic, but it's not enough of a priority for me to drag out the perf board.

                        I am getting the LCD on order though.

                        Comment


                          #92
                          Re: New tool to find short capacitors on motherboards : shorty with display

                          it's an OLED - get a selection of white, blue and mixed colour.
                          i wish they sold them in green - it would look like an old crt

                          Comment


                            #93
                            Re: New tool to find short capacitors on motherboards : shorty with display

                            Originally posted by stj View Post
                            it's an OLED - get a selection of white, blue and mixed colour.
                            i wish they sold them in green - it would look like an old crt
                            I have this one in my cart. Not sure I want to go back to the old days with a choice of monochrome green or monochrome amber. I don't miss that at all.

                            https://www.aliexpress.com/item/3280...c00gcT6Vz&mp=1

                            Comment


                              #94
                              Re: New tool to find short capacitors on motherboards : shorty with display

                              @Kripton2035

                              Hi Kripton.... it's August now !! Please say you have more information on the PCB supply - or anything about this project. I can't wait to build one !

                              Comment


                                #95
                                Re: New tool to find short capacitors on motherboards : shorty with display

                                Originally posted by aneng View Post
                                @Kripton2035

                                Hi Kripton.... it's August now !! Please say you have more information on the PCB supply - or anything about this project. I can't wait to build one !
                                My LCD for this project just arrived today, it's much smaller than I thought it would be. This project should be able to fit on some perfboard. If you want to build it on some perfboard, I'll go along. Last I heard there was one last issue, and kripton was busy at work. I'm sure he will come back when he's through.

                                Want to work through the last issue?

                                Comment


                                  #96
                                  Re: New tool to find short capacitors on motherboards : shorty with display

                                  nice job..

                                  Comment


                                    #97
                                    Re: New tool to find short capacitors on motherboards : shorty with display

                                    Any progress?

                                    Comment


                                      #98
                                      Re: New tool to find short capacitors on motherboards : shorty with display

                                      not here - maybe check the thread at eevblog?

                                      Comment


                                        #99
                                        Re: New tool to find short capacitors on motherboards : shorty with display

                                        From eevblog:

                                        "sending good with a value from france to outside of europe (even into europe) has become a pain in the a** since january 2021 and new EU VAT rules.
                                        it will be easier for me, and cheaper for everyone, to sell a gerber file of the pcb, and people ordering 5 pcb from jlcpcb or like.
                                        instead of me collecting many pcb's and sending them one by one to the world."
                                        I could contact him and get some sent to me and send them out to others (US only) if there are enough people interested.

                                        Comment


                                          Re: New tool to find short capacitors on motherboards : shorty with display

                                          Yes the new EU VAT rules (January 1 or Jun 1, 2021) are a really f*cking pain in the a**.
                                          No more exclusion on small values (less than 20€, including shipment).
                                          In practice, this means that even end consumers and non-profit receivers / senders in the EU must handle themselves all bureaucracy and collect/deliver all VAT values to EU member State, plus a fixed fee to local/end carrier.
                                          What a f*cking mess!

                                          Comment

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