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Aixun T3A overshooting?

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    Re: Aixun T3A overshooting?

    I don’t think it’s got to do with power, I’m barely touching some specific joints. I’ve done the ‘coin’ test with lots of solder and I can dip the tip in a wet sponge and it doesn’t happen.

    Yes it’s brand new so o guess I’ll ask for a replacement, wish me luck.

    Still, I can’t think of what could be sensing that is triggering that behaviour.


      Re: Aixun T3A overshooting?

      I have an update. It's ground.

      When the PCB I am soldering is grounded, SOME solder joints will cause havoc.
      AND, the handle is buzzing.


        Re: Aixun T3A overshooting?

        contact Aixun - it's gotta be a psu issue
        my guess is the ceramic capacitor between the primary & seconday is missing or the unit is missing a ground connection between the mains earth input and the handle somewhere.

        can you use your meter to check resistance between the iron tip and the earth pin on the back of the unit - earth on the iec connector i mean.
        while your at it - check your power cable and your house socket

        i'v had a few recent "incidents" with power cords with molded plugs on them!!!!
        if you buy anything high wattage with a molded plug - check the plug isnt getting hot while it's running - specially fan heaters from Lidl!!


          Re: Aixun T3A overshooting?

          Shall do, I did check that the unit was earthed, I believe everything reads full continuity but the tip which is reading some resistance but not much? I'll double check.

          Bear in mind that when I touch ground directly with the tip, it does not happen. It only happens when touching SOME solder joints on an earthed PCB.

          I'm not sure about the PSU to be honest. The display would show "undervolt" or something like that, like it does for a brief moment when you power it off.

          Someone on EEVBlog says this is normal - I can't accept a soldering iron which cannot be used on grounded equipment, would you agree?


            Re: Aixun T3A overshooting?

            it makes no sense.
            the tip resistance to mains earth should be almost zero

            *unless* it's floating for safety - but i dont think they did that.
            weller in the past used to connect the tip to mains earth through a parallel resistor and capacitor to limit current incase you accidentally worked on something live.

            i modded my t12 the same way - sometimes i can get leds to glow while soldering them now!


              Re: Aixun T3A overshooting?

              Is the device you solder on connected to power mains? Other than that it doesn’t make any sense what your saying. None of my soldering irons do that.


                Re: Aixun T3A overshooting?


                no power, just ground. No batteries on the board.

                And if someone said "disconnect it from ground" then my question is "so the T3A won't work when I am pre-heating a board as the pre-heater is grounded".

                Do you have a T3A as well?


                  Re: Aixun T3A overshooting?

                  Please do some measurement, voltage and current (carefully) accross your ground clip and soldering tip, both ac and dc?

                  Also check voltage of your ground clip against mains socket, with one pin should be 240v and with another 0.0v (earthed from distributor)
                  Last edited by harp; 09-16-2023, 05:48 AM.


                    Re: Aixun T3A overshooting?

                    Here are the measurements

                    GND to TIP resistance is 0.7Ohm when the station is off (my leads read 0.4 Ohm when shorted).

                    If I take the tip to 100C and then ask the station to go to 400C - so the tip is heated constantly for a few seconds - during that time my Fluke measures OL.

                    When the tip keeps the temperature steady, resistance jumps around, clearly when the tip is being heated continuity to ground is lost??


                    GND to TIP: 0.584V AC when heating (same trick than before)
                    GND to TIP: 0.915V DC when heating (same trick than before)

                    GND to TIP: 1.5A DC when heating (same trick than before)
                    GND to TIP: 1.74A AC when heating (same trick than before)

                    MAINS check
                    The chassis is indeed grounded and the GND clip too.

                    station GND to Mains GND: I do have continuity
                    Station GND to Mains: 0.26AC on one mains leg and 242VAC on the other.

                    I'm not sure I should read that amount of voltage and current on a soldering iron to be honest. My older iron doesn't read anything like that, it reads 0V at all times.


                      Re: Aixun T3A overshooting?

                      Station GND to Mains: 0.26AC on one mains leg
                      Ground clip is mounted on station gnd? (that black aligator ground clip that you show on video)
                      I ask because it is possible that ground clip have loose resistive conection with wire - ground clip must be 0.0Vac to earth ground, otherwise it is not well grounded.

                      The measure is very suspicious, its look like major leaking, and I am not expert to give value conclusion, but yout tip may damaged some sensitive devices, maybe is best to do not use that soldering station till somebody with identical model compare and confirm measure reading...
                      Last edited by harp; 09-16-2023, 04:52 PM.


                        Re: Aixun T3A overshooting?

                        Yes ground clip is mounted on the station. I used that for my measurements as I read 0.7Ohm with mains ground so it does seem to be a direct connection.

                        I thought the same, that station would be able to damage some sensitive stuff.

                        I hope someone can help me, I have to get back to the seller tomorrow though to report the issue. I'll make a video explanation and let's hope they don't BS me or offer a partial refund...


                          Re: Aixun T3A overshooting?

                          Originally posted by tony359 View Post

                          no power, just ground. No batteries on the board.

                          And if someone said "disconnect it from ground" then my question is "so the T3A won't work when I am pre-heating a board as the pre-heater is grounded".

                          Do you have a T3A as well?
                          Yes, I do have the T3A and run the T245 and the T12 pens and elements. I can solder copper pipe, or something that has a ridiculous heat sink on it with my T245 no problem.

                          Look for something copper that is bigger like a copper pipe / sheet and see if you can solder to that.

                          When I saw your video, it seems like each time the T3A heated the pad a bit harder, I could see the T3A ramping up heat fast and in the peaks is seems to go “crazy”. Yours does it every time the power demand from the pen is high. Check it out and see if you can verify this.


                            Re: Aixun T3A overshooting?

                            Originally posted by CapLeaker View Post

                            Look for something copper that is bigger like a copper pipe / sheet and see if you can solder to that.

                            I believe you might be suggesting that the issue happens when the PSU is being driven harder.

                            I can assure you this is not the issue. On the latest video I am barely touching a small solder joint - it doesn't melt as there is no flux and it's oxidised - and it misbehaves immediately. The spike you see on power is caused by the issue and not vice versa. The very same solder joint doesn't trigger the issue when the PCB is not grounded.


                            Anyways, yes I did try the 5p copper coin test. I've melted 10cm of solder on a 5p coin and waited until it flows on the whole coin. It takes 40 seconds while with my old station it takes 100 seconds. That's why I really like the T245!

                            But I am pretty confident it's not the PSU.

                            It sounds like you've never experienced this issue yourself - would you think you're soldering on grounded PCBs sometimes? Again, it's not touching ground itself which causes havoc.

                            Thanks for now!


                              Re: Aixun T3A overshooting?

                              Yes ground clip is mounted on the station. I used that for my measurements as I read 0.7Ohm with mains ground so it does seem to be a direct connection.
                              This is not solve your problem, but be aware of chinese creativity - they may using a aluminium or ferrous wire instead of copper, and to do so is offen only plated with copper to look like copper wire... the wire have noticable resistance (about you measured) and heating while carry more amps (car bulb etc). Also, they regulary ommit soldering wire to aligator clamp, and contact is not reliable, like to coroded due to difference in material potencial...

                              On pictures is wire that hang on regular magnet - this is my test and later I do a label of this wire with "Fe".
                              Attached Files
                              Last edited by harp; 09-17-2023, 08:48 AM.


                                Re: Aixun T3A overshooting?

                                thank you - I am aware that by buying on Aliexpress it's a shot in the dark.

                                Just so that I understand correctly, what you point out is not relevant to the issue I am experiencing, just a general comment, am I correct?