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    Troubleshooting Uni-T EEPROM ErrE

    I've got a UT139C that powers on for a second with an ErrE, before switching itself back off.

    I haven't found much information about this, other then the error being caused by the EEPROM (both on the internet and from fellow members here). While I'm using a cheaper multimeter temporarily, I'm trying to troubleshoot this... hoping it won't go to trash

    I've opened it up and did a visual inspection. Unfortunately I couldn't see anything obvious, everything looks clean and as new. No signs of damaged components.

    I'm attaching two photos: one of the eeprom area, and the other I think are the rails on the back that end up to the eeprom (?). Also attaching datasheets.

    And because I'm doing this to learn, and I'm still new to this, I have a couple questions.

    1. What are the components starting with L? I know C are usually caps, while R are resistors, F fuses and so on.
    2. Laugh at me, but, where do you find ground on these 2 layer boards? On laptops it's easy cause these are usually screw holes/ports etc.... What am I missing?

    Thanks a lot
    Attached Files
    Last edited by DanFen; 01-06-2022, 05:12 PM.

    #2
    Re: Troubleshooting Uni-T EEPROM ErrE

    Look here
    https://www.eevblog.com/forum/testge...matics-avail)/

    Comment


      #3
      Re: Troubleshooting Uni-T EEPROM ErrE

      L are inductors.

      do you have an eeprom programmer?

      Comment


        #4
        Re: Troubleshooting Uni-T EEPROM ErrE

        Thanks, will go through it.
        Hello again! Not yet, but on delivery. Went for the RT809F.
        Originally posted by stj View Post
        L are inductors.

        do you have an eeprom programmer?

        Comment


          #5
          Re: Troubleshooting Uni-T EEPROM ErrE

          Here are two original and modified firmwares for UT139C.
          Attached Files

          Comment


            #6
            Re: Troubleshooting Uni-T EEPROM ErrE

            backup the original first, it has calibration data in it

            Comment


              #7
              Re: Troubleshooting Uni-T EEPROM ErrE

              I know it's been a while, but I just got to do this now. Wrote the shared bin to the IC, re-soldered it back, and still getting the same error :/

              I also de-soldered the IC and read it again just to make sure that it got programmed correctly. Then compared it to the shared hex and they are the same... which concludes that the programming was fine.
              Last edited by DanFen; 07-16-2022, 02:51 PM.

              Comment


                #8
                Re: Troubleshooting Uni-T EEPROM ErrE

                Post the EEPROM file you have, to see if it can be fixed.

                Comment


                  #9
                  Re: Troubleshooting Uni-T EEPROM ErrE

                  This is the backup (the one I had before I wrote the shared one).
                  Attached Files

                  Comment


                    #10
                    Re: Troubleshooting Uni-T EEPROM ErrE

                    check the tracks between the eeprom and the main chip.
                    here is a schematic of another meter with the same chipset,
                    and a datasheet with example schem on page 17
                    Attached Files

                    Comment


                      #11
                      Re: Troubleshooting Uni-T EEPROM ErrE

                      Will try Is that done with the EEPROM back in circuit?

                      Originally posted by stj View Post
                      check the tracks between the eeprom and the main chip.
                      here is a schematic of another meter with the same chipset,
                      and a datasheet with example schem on page 17

                      Comment


                        #12
                        Re: Troubleshooting Uni-T EEPROM ErrE

                        I looked at your EEPROM dump with a hex editor and did not see any errors. I can't know what every byte should be, but I did not see anything corrupt.
                        Check the EEPROM pullup resistors on SDA and SCL are OK, is R29 soldered on both sides? The main IC DTM0660 looks like solder balls are behind/under the pins?

                        Comment


                          #13
                          Re: Troubleshooting Uni-T EEPROM ErrE

                          Thanks for checking!

                          All resistors seem to be soldered fine, but I'll re-flow them just in case. I also measured them and the readings are good.

                          About the solder balls, do you mean in between pins? If so, it doesn't seem like it under the microscope, and I didn't reflow it or touch it in any way.

                          I also tested in continuity between the DTM0660 and the EEPROM IC, in case there's a broken trace, but all seems fine.

                          Originally posted by redwire View Post
                          I looked at your EEPROM dump with a hex editor and did not see any errors. I can't know what every byte should be, but I did not see anything corrupt.
                          Check the EEPROM pullup resistors on SDA and SCL are OK, is R29 soldered on both sides? The main IC DTM0660 looks like solder balls are behind/under the pins?

                          Comment


                            #14
                            Re: Troubleshooting Uni-T EEPROM ErrE

                            No, the solder bridges I see are UNDER the pins.
                            You can poke a wire or paper clip (gently) through and see if you hit them. Usually they are solder balls from extra paste and can poke out.
                            Attached Files

                            Comment


                              #15
                              Re: Troubleshooting Uni-T EEPROM ErrE

                              Doesn't seem to be the case, must be the quality of the previous photo

                              I'm still to re-flow the resistors around the EEPROM area.

                              Originally posted by redwire View Post
                              No, the solder bridges I see are UNDER the pins.
                              You can poke a wire or paper clip (gently) through and see if you hit them. Usually they are solder balls from extra paste and can poke out.
                              Attached Files

                              Comment


                                #16
                                Re: Troubleshooting Uni-T EEPROM ErrE

                                Reflowed the resistors, still the same. While it seems to be interesting, I don't think it's worth working on it anymore. The only thing I miss about this is that it has auto range, and the other ones I have do not.

                                Comment


                                  #17
                                  Re: Troubleshooting Uni-T EEPROM ErrE

                                  did you check the eeprom is getting power?

                                  Comment


                                    #18
                                    Re: Troubleshooting Uni-T EEPROM ErrE

                                    For some reason EEPROM power has a R40 100Ω resistor to +V, and it's supposed to have a bypass cap 0.1uF across power and gnd but I don't see it.

                                    Comment


                                      #19
                                      Re: Troubleshooting Uni-T EEPROM ErrE

                                      Check with an oscilloscope the data line, clock and the main oscillator for activity.

                                      Comment


                                        #20
                                        Re: Troubleshooting Uni-T EEPROM ErrE

                                        Please help....

                                        Does anyone here have the working and original firmware of ut139???

                                        Comment

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