A lot of people come to my shop asking me if I can repair electronic welding machines and I have no clue how to do that, I have no clue how they work therefore I can not fix them. This time I was eager to find out how they work and how I can repair them. A guy who knew my brother came to my shop asking me to repair this electronic welding machine for him.
The moment I turned it on, I could hear the fan running, so I opened the cover and took a look inside to see what I am dealing with. There were about three electronic boards there and components that I am very familiar with. I took it next door to my brother workshop (my brother uses this kind of machines so he is very familiar with it). He hocked up the welding cables and tried to weld with it but it did not work, there was a red LED on board that was on but flickering and the green power led was not on which gave me the indication that there is something wrong with the power supply.
I took it back to my work shop, took the power board off and started testing. I noticed the main capacitor was holding the charge. I discharged it and started testing the component around it. I tested it with a LOPT/FBT meter and it did not give me full bars so I was suspecting some bad component like diodes, main capacitor and MOS N FET some where in the area. After some testing I found a diode that was shorted out in the secondary side of the power supply. It was market with HER 206, so I replace that with HER 203 and tested again with LOPT/FBT and still did not get full bars on it. I noticed that the main capacitor was starting to bulge just a little bit. It was 47uf/400 volts so I replaced that with a new one. When tested with the LOPT/FBT meter, it was not give me full bars yet and when I turn the machine on, the main capacitor was still holding charge. After a deep checking with a strong magnifying lens, I found out that there is a line on the opposite side of the board that connects the main capacitor positive leg to the MOS N FET was not soldered right and I thought that is why the main capacitor was holding the charge.
Once I re-soldered that, the machine worked and I could see the green power LED coming on. I took it to my brother’s shop and tried it again and this time, the machine worked just fine. I was really happy to see it come to life. I worked on that machine for about four days and finally got it fixed.
The guy came and picked it up and he said that he has more of this machine to be fixed. It was a challenge and now it is becoming a source of income for me. That is really great.