A regular customer brought a welding machine for repair. As explained by the customer, this welding machine powers up fine and the green comes on as usual but when it comes to welding, it was very weak.

By the look of it I can tell it was maintained by someone else.

It was clean and nice but I am guessing, the other technician was not able to figure out the problem of weak welding.

As you can see, the power light comes on but that is about it. The fan kicks in fine and I could read 57 volts on the positive and negative terminals of the machine. With all that in mind and in reality, what could be the problem of weak welding?

This is another reason why I think that someone was trying to fix this machine and obviously that technician failed. That kind of, put me in a nasty mood but at the same time, I am going to do my best to repair it and prove that I can do it. It was a big challenge because I never experienced this kind of issue before.

In order for me to get to the top side of the board, I had to take these screws off.   I am trying to reach the amp potentiometer socket and trace that so I can find out what is wrong. There are more screws on the other side of the machine as well.

As I took the board off, my main target area was to the right side of the photo. It is marked in red. I have to check all that area to find the fault.

If nothing is faulty there, the only thing left to check was the main computer logic board and that would not be a good sign since these logic board are hard to find or repair.

If you look to the arrow on this side, there is a transistor SS8050. That is an NPN transistor and connected directly to the white socket of the amp potentiometer. When I tested it, there was no reading whatsoever. I was really happy to see that because I believe that was the main cause of the problem.

As I installed the replacement on that board and put the machine back together. I took it to my brother next door and he gave it a try and guess what it worked nicely. Sorry I could not get a photo of it, I totally forgot about that.

The customer came and got the machine. He was surprised that it worked. I did not have to say anything because my work said it all. 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:

https://www.electronicsrepairfaq.com/one-bad-s9013-transistor-caused-no-charging-in