Help Kempomat 250C

  1. Edgard New Member

    Dear good evening, I am new here looking for help, please be good, I turn to you because I need to be able to operate an old Kempomat 250C machine, the problem is the following described in the attached drawing, the A001 card (4256050) is apparently damaged Because it does not deliver 24 V for K001 to work, the card looks simple but I still can't find the problem or damaged component.
    That is why I turn to you, for help I do not know if there is a schematic with the components to be able to make a better review of each component or as a replacement the card to be able to import ... by the way I write to you from Chile here it is practically impossible to get help for these products they are only interested in selling a whole new team, as you will understand that is really depressing.
    I hope you can help me.
    Best regards.

    P.S. sorry for my english i am using google translate.
    • IMG_20201017_145648 (2).jpg
    • Esquema.jpg
  2. eddie49 Member

    Even without a full circuit diagram of the A001 printed circuit board ( PCB ), I'm sure that you will soon be able to make progress in locating and fixing this fault.

    In addition to the Contactor K001 ( main relay ), the 24v auxiliary power is also used to run the wirefeed motor, via the speed control circuit on the PCB.
    Although there is no arc ( since the relay does not close ), does the wirefeed motor turn when you press the torch trigger? Does the gas valve open?

    If neither the relay, the wirefeed motor, nor the gas valve are working, you need to confirm that the torch trigger switch is closing properly. Check by using a piece of wire to short between the two small pin receptacles at the Euro socket. Then trace the wires from the Euro socket to the PCB, short them at the PCB pins. From the diagram, there appears to be a thermal overload switch ( thermostat ) in that torch switch circuit - check that it is not open-circuit.

    If the trigger switch circuit is good, a failure of all three of the functions of the PCB ( relay, wirefeed motor, gas valve ) would indicate a problem with the DC power on the board. The AC input to the board from transformer T002 ( which you have checked is OK ) will be rectified on the PCB by the 4 large diodes at the bottom left corner of the photograph. Is the nearby fuse OK? The DC output from this bridge rectifier is probably smoothed by the adjacent blue capacitor. Check the rectifier output, and the voltage across that capacitor, and also the other one at the left centre of the board.
    Some of the flat TO-220 style components, mounted on heatsinks, may well be voltage regulators, e.g. 7824, 7812, or 7805. For this type of regulator, pin 1 ( left ) is the input, 2 is ground, and 3 is the regulated output.

    Depending on the results of the previous suggestions, the next step would be to investigate the relay drive circuit. The K001 relay will be switched on by a power transistor on the PCB. Trace the wires from the relay coil to the pins on the PCB, then visually follow the tracks on the PCB to the relevant component - it will be TO-220 style, mounted on a heatsink. From the part number, it should be possible to find the pinout of this device, and check the control signal on the base pin.
    James1979 and angellonewolf like this.
  3. Edgard New Member

    Dear friend Thank you very much for your prompt response, right now I am about to follow your suggestions and I will document the steps which I am going to upload here in the forum ... thank you very much
  4. eddie49 Member

    I forgot to mention that the thermal overload switch may be located on the main welding transformer. It can be glued to the outside of the winding, or even buried deep inside. There may be another thermal switch on the heatsink of the main welding rectifier. They often look like this: images.jpeg
    Overtemperature will open the circuit between the 2 pins. They can stick open. Check with an Ohmmeter, or simply bypass by joining the two wires together.
    Good luck with your investigation!
    a111r likes this.
  5. Edgard New Member

    Dear edduie49 good days, I must tell you that yesterday at the last hour of the day the machine worked! She is ALIVE again ... the problem is that I don't know what happened!
    detail of what has been done:
    1- check thermistor = ok
    2- contactor K001 = ok
    3- Blue capacitor power source = ok
    4- triac = ok
    5- check everything that I could overlook I did not find anomalies,
    once you check, mount everything again and short-circuit the torch input according to you. He indicated to me, this action closed K001 closing its circuit and making the feed wire spool motor move, at first it advanced for a few seconds and stopped, then I told myself the torch trigger is bad but to my surprise it was fine at disassemble and check cables and switch, connect the torch to the machine I was able to pass the filler wire and the machine no longer stopped advancing the filler wire ... so I don't know what could happen that now works, unfortunately I couldn't test welding since I run out of shielding gas in the week I should get a cylinder.
    In summary I do not know what could happen after being completely dead yesterday it worked again and that has me puzzled ... that I can tell, I will see how it behaves when the shielding gas arrives in the week.
    Greetings again and thanks for the help.