A Welding Machine Powers On But Does Not Welled Repaired
A regular customer brought this welding machine for repair and according to what I saw when I powered it on, (power switch was not active) there was either a short or some overheating going on inside the machine. Let us find out what kind of fault was it.
According to specs, the green light is suppose to come on as an indication that the machine was on but the red right is not suppose to come on unless there is a fault going on inside the machine and that is for protection.
Usually when I see this kind of fault, I usually head to the main Mosfets and look for shorts there but to my shock all Mosfets checked out fine.
While I was checking inside this machine, I saw this; someone was inside this machine and actually disconnected the power switch and connected the main power wires directly to the main power board.
That explained why the power switch was not active when I first power up the machine.
As I was checking the welding boost circuit which is connected to the main Mosfets, I saw this. The two red wires melted and shorted together and that explained why this machine indicator was showing a short inside the machine. One of the red wires was also loose not completing the welding loop.
The black and red wires are connected to the welding transformers that sit beneath the heat metal of the Mosfets. When testing the black and red, it was showing a low resistance and that is what I am supposed to get on both transformers.
Since the two red wires were shorted together, the machine was protecting itself by indicating a red over heat signal not allowing the machine to go ahead with the welding process.
As you see in the photo, a surgery was done there to bring the welding machine back to life.
The moment I separated the two shorted red wires and repaired the fault, the overheating indicator was back to normal and because of that I was getting a normal voltages are the positive and negative terminals of the welding machine.
The customer insisted not to install a power switch against my recommendation due to the fact the power switch always fails and constantly has to replace it. I offered to install a higher amp rated switch free of charge but still he did not agree. It is good idea to have a power switch to on and off the machine while it is connected to AC source. It is his decision and he will take responsibility for it.
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: