A Dead Welding Machine Was Brought Back to Life. Model: Apex SMINI-180
A welding technician brought this welding machine to my shop for repair. I powered on the machine using a current limiter and I could not see any sign of life on that machine.
I took the cover off and right away I saw a broken fan; with a broken fan usually overheating; with overheating there will be IGBT shorted so let the fun begin.
Before I started the repair cleaned the device thoroughly and everything seems to be in good order except one thing, one capacitor was missing in the machine to discover later on that there were only two capacitors in this machine and that is how it was made in the factory.
Something is wrong here; do you see the fault? That is not an original fan; this kind of fans is used in desk top computers and it does not provide enough air for cooling in any welding machine.
When checking IGBT’s I found two of them shorted and needed replacement.
Before replacing the faulty parts, I had to do component checking around that area making sure that on the outside pins of every IGBT has the same resistance reading otherwise there are shorted parts somewhere in the device.
In this case I found only two IGBT’s shorted with part number MP40N65BU and I was ready to install the new parts in when I realized I do not have the same IGBT’s needed for replacement. The original part uses 40 amps 650 volts. The ones that I have in the shop are 40N60 which is 40 amps 600 volts. The voltage rating on the replacement is 50 volts less than the original ones. I consulted a friend of mine about it and he said it is ok since these tiny machines usually do not reach the 600 voltage limit so I went ahead and used the replacement.
I installed the first and the second IGBT and replaced the fan as well. I used the right fan this time to provide the right cooling for this welding machine.
I installed the fan wire connections to do the testing and make sure that all is well.
I took the machine to my brother next door to make sure all was working well and it was. I called the customer for pick up and when he came he wanted to test it himself as well and he was happy with outcome.
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 article on A Turkish Made Welding Machine That Was Shorted, Repaired and Maintained
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Albert van Bemmelen
December 14, 2024 at 4:16 pm
A wrong replaced fan in this welding machine that caused the shorting IGBT's was luckily professionally repaired again. And good to know that the 600V IGBT's also qualify as replacements.
Waleed Rishmawi
December 14, 2024 at 6:08 pm
Albert: the IGBT requiers cooling otherwise it will go short due to excessive heat and when putting the wrong fan that is does not provide enough air flow is even worse. have a blessed day