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K2837 FET shorted in Welding Machine Repaired

By on January 16, 2021
welding machine repair








A welding technician brought his welding machine for repair. The guy explained that this machine went dead while he was doing a welding job in a village nearby.

how to fix welding machine

It was no brand welding machine because the cover was off and all I can see was dirt, dust but the PC formation was kind of familiar to me.

I dusted off the machine and headed directly to where the parts are usually failing on this device.

bad caps in welding machine

As I was getting ready to do some checking, I saw this damaged area in the power supply of the welding machine. As you can see, one of the main capacitors was just laying there assuming someone was already in this machine.

bulged cap in welding machine

It was already bulgy and needed replacement.

It was 470uf/450 volts which I have plenty of in my shop.

bad caps in welding machine repair

I took the power board off and soldered a new capacitor on. I did not power on the machine. A damage like that could have caused one or two of the Mosfets to be shorted out or even burnt out.

how to fix welding machine

And as expected, one was shorted out in this high tension area and it had to be replaced. The part number is K2837.

k2837 datasheet

Click on the photo above to access K2837 datasheet

The part was replaced and the machine was tested but sad to say I forgot to take any photo of that. The customer was happy with the outcome because he came and tested it out himself and to that I could say

Mission Accomplished.

This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.

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Note: You can check his previous repair articles in the link below:




  1. Albert van Bemmelen

    January 16, 2021 at 9:16 pm

    it is a shame that they bring defect devices this dirty without cleaning them first, and worse that they use the welder constantly without any protective cover. If they had an air compressor to blow it clean first that probably could have even looked dirtier in this case. Thanks for sharing the repair and the new mosfet datasheet!

    • Waleed Rishmawi

      January 18, 2021 at 2:17 pm

      Albert: indeed. the abuse of such machines is beyond my understanding and I see that a lot sad to say. I do the cleaning fixing and send it back in good shape but the customer does not appreciate that and does not take care of his machines that bring him business. have a blessed day.

  2. Parasuraman S

    January 16, 2021 at 9:38 pm

    Yes, I too endorse the comments of Albert! Why these guys abuse their tools to this extent, just beats me! Anyhow, it brings devices to you for repair and ensure your earnings! Anyhow, many thanks for sharing yet another welder article!

    • Waleed Rishmawi

      January 18, 2021 at 2:18 pm

      Parasuraman: I know the feeling. you are most welcome my friend. have a blessed day

  3. Yogesh Panchal

    January 17, 2021 at 1:07 am

    Running high current equipment without cover.. these guys are playing with their and others life..................
    Please take care while blowing up the dust use proper face mask.
    this dust is very dangerous for lungs....

    • Waleed Rishmawi

      January 18, 2021 at 2:19 pm

      Yogesh: yes indeed. I never do cleaning or blowing away dust without the proper precaution. have a blessed day

  4. Gassan Ali

    January 17, 2021 at 11:13 am

    Nice work. I keep an eye on the part numbers that you mention because I know they are super-duper important.

    • Waleed Rishmawi

      January 18, 2021 at 2:21 pm

      Gassan: thanks man. these mosfets are very important in every welding machine. every machine has different mosfets and keeping them in stock is a challenge. have a blessed day

  5. Humberto

    January 18, 2021 at 3:21 pm

    Good repair Waleed. You are a Master when it comes to Welding Machines

  6. Waleed Rishmawi

    January 20, 2021 at 5:54 pm

    Humberto: thanks man. I do what I can to get them fixed. have a blessed day


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