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A Shorted Welding Machine Repaired. Model: Apex

By on May 7, 2023
A Shorted Welding Machine Repaired. Model: Apex

apex welding machine repair

Yes I repair a lot of Apex welding machines but this is the first time I got a big one for repair.

how to fix apex welding machine

arc 200 repair

If you look to the red light on the right of the screen you would find it on, an indication that something is shorted and most likely IGBTS.

igbts shorted

The current limiter light bulb is lit brightly and that is a confirmation of shorted parts.

fixing welding machine

Someone has been in this machine and it was clear to see since one of the IGBT’s has fresh solder on it. The customer confirmed that because he sent it to another technician but could not repair it simply, he did not have the replacement parts at his shop.

Later on that day I got a call from a friend of mine who is also a technician and he informed me about this welding machine. He took the shorted IGBT out and tested it and informed me that all of the IGBT’s in this machine are shorted and needed replacement. He also warned me that the customer is very picky about the repair cost and told me to discuss the price with the customer before any attempts of any repair on this machine.

I called the customer and discussed the price (I always do that before any repair) and we reached an agreement so let us begin.

how to fix a broken welding machine

The board of this welding machine is very different from the ones I usually work on but the parts number are the same. And yes, all IGBT’s in this machine were shorted and needed replacement. Part number is FGH40N60SFD.


I found chicken feathers inside the heat sink that the IGBT’s attached to and the thermal paste on these parts was dry.

FGH40N60SFD shorted


Click here to access the FGH40N60 Datasheet

I already have these parts available in the shop so I cleaned the area, added fresh thermal paste and installed new IGBT’s in place.

how to repair apex welding machine

Before attempting to power on the welding machine, I usually do this ohm check between IGBT’s pins and I should get the same ohm readings otherwise something is shorted (usually SMD parts in the same circuit).

All readings were OK.

testing output voltage of welding machine

Through a current limiter I powered on the welding machine and if you noticed that the light on the right side of the photo is not on any more, an indication that the short was gone and instead, the power light was on.

light bulb On testing for repair

Also the current limiter light bulb was very dim another indication all is well and it was safe to test the machine next door with my brother.

how to test dc output of welding machine

I was getting the right voltage but not through a current limiter this time. I took it next door for my brother to try and test and make sure all is well.

Of course everything was according to specs and to that I could say:

Mission Accomplished.

waleed Rishmawi

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.

P.S- Do you know of any your friends who would benefit from this content that you are reading now? If so, forward this website to your friends or you can invite your friends to subscribe to my newsletter for free in this Link.

Note: You can check his previous article on PS4 Controller That Does Not Charge Repaired



  1. Albert van Bemmelen

    May 7, 2023 at 2:14 pm

    In my town and probably my country Welding machines like these with Max currents of 29 Amp at 230VAC input are impossible to use on our power outlets at home! The 29A x 230V equals about 6670 Watt! While our power lines only support 16A rated fuses which equals to only 3680 Watt of maximum power!
    Not even my China made Sunkko 709a spot welder for 18650 precision welding can be used safely without blowing the main power fuse! Which in that case is a very costly mainpower fuse replacement I can't do myself! The Sunkko easily dissipates well over 4 KW of power which is already way over the maximum of 3680 Watt! Why I only can use this machine safely for a very short period of time with a current limiter for safety. And only after about 30 seconds of welding I need to let cool off the limiter every time for at least 30 minutes before it can be used again! Which makes it a useless spot welder!

    • Waleed Rishmawi

      May 8, 2023 at 2:49 pm

      Albert: thanks for sharing that information that is new to me. how would they weld if the amp is too low. 29 amp is very low when it comes to welding. these machines that I repair goes up to 200 amp or even more. have a blessed day

  2. Parasuraman S

    May 7, 2023 at 8:09 pm

    That was a grand fix! It is unfortunate that while customers love to make more and more money using a device, they are very stingy when it comes to its repair! They think that we, technicians, are very cheap stuff, and do not consider we too have equal or more commitments like them. There are still a few who pay the price for quality service.

    • Waleed Rishmawi

      May 8, 2023 at 2:55 pm

      Parasuraman: thanks man. totally agree with you there. some customers not willing to pay the right price for the repair and on ther other hand, still customers out there so kind and thoughtful when it comes to the time spent on the repair and willing to pay money even if the machine is not fixed. I am trying to inforce some kind of policiy on repair estimate fees, many people are rejecting it and a lot of people accepting it and I was happy to see that. I told them ahead of time about the estimate fees and it is working fine so far. have a blessed thought and thanks for your input

  3. Imoudu.O

    May 8, 2023 at 4:20 am

    You are right Mr P.S,I remember a customer once ask me to repair a backlight tv problem without any down payment which I basically refused.The tv was with me for almost 6 months b/4 paying and yet to complete payment,but have collected tv about 5 months ago.

  4. Imoudu.O

    May 8, 2023 at 4:21 am

    Thanks for sharing Mr Waleed and have a nice day

    • Waleed Rishmawi

      May 8, 2023 at 2:57 pm

      Imoudu: you are most welcome. you too have a nice blessed day

  5. Mathew Charles Karonga

    May 8, 2023 at 9:36 am

    Greetings Everyone

    Thank you for a detailed explanation on how you repaired the welding machine and it was so helpful and you are always there to refresh our minds on steps of troubleshooting the Welding machines.

    Keep sharing your knowledge

    stay blessed

    • Waleed Rishmawi

      May 9, 2023 at 1:38 pm

      Mathew: you are most welcome and very happy you are enjoying the articles and learning from them. keep up the good work and apply what you learn in a practical way because that is the best way to learn and stay updated on the repair. have a blessed day

  6. Lao young

    May 11, 2023 at 9:20 pm

    Thanks for the lesson. I will use the knowledge in repairing my plamas cutter..... the in sight

  7. Yogesh Panchal

    May 17, 2023 at 11:33 pm

    Excellent! as always Waleed.


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