A Welding Machine With Overheating Issue Repaired
A welding technician brought in this welding machine for repair. It is a different kind of welding machine but still good brand and a good quality device.
I have worked on this kind of model before so it should be an easy repair. When I powered on the device right away I got a warning light which is an indication of overheating which means shorted parts on board.
Usually when I get the overheating light, the machine would not even start; it is kind of a way of how the machine is protecting itself from further damage. From experience when getting such warning it is usually the IGBT/Mosfet shorted out in the device.
Few screws out and I was able to take the top cover off exposing the inside board. In this machine there are two boards, one in the bottom and one on the top.
That is the top board which controls the display and the amp variable resistor; in other words the amp potentiometer.
Once the top board was disconnected from the machine and I took the main board out it was time now to check for shorted parts.
I took one of the IGBT’s out and tested and it was shorted.
I checked the SMD parts around that part and found everything to be ok.
The part number is GW40V60DF and from experience, if one is shorted there will be one on the other side of the board shorted as well and that is exactly what I found.
I usually replace the four IGBT’s here but when I called the customer he did not want to pay the full amount for repair and he wanted only the faulty ones to be replaced. I tried to explain that it is better to replace all of them but he insisted on replacing only the faulty ones and that is exactly what I did.
I replaced the faulty ones as see in the photo and soldered them on board. Before powering on the machine I checked around the second IGBT for faulty SMD components and found all of them to be ok.
Through a current limiter I powered on the machine and as seen it powered on just fine and the overheating indicator was off and that was pleasant to see.
I powered the machine normally and got reading on the output terminals of the machine and that is a very good reading. I took it next door to my brother to check the machine and he gave me the thumps up and that put a smile on my face.
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 article on A TV With Faulty Backlight Repaired And Maintained