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A Welding Machine With The Amp Display Cannot Be Controlled. Model: Delta mmA200

By on January 20, 2024
how to fix welding machine







A guy who lives in Jerusalem experienced this kind of fault in this welding machine and called me right away to bring it over so I can take a look at it.

how to repair and fix welding machine

If you look at the amp knob, it is set on 120 but the display is still showing zero and when I tried to weld with it, the amp was too low to do any kind of welding. That gave me indication that the fault was not the actual display but the amp setting circuit in the machine is faulty and needed some attention.

The customer is a pipe welder and this machine is urgently needed so I started right away to do some checking and voltage reading in it.

fixing welding machine

Look how dirty the welding machine was so I cannot do anything kind of repair or check up till I blow away all that dust and dirt so I can see what I am doing here.

repairing welding machine

I am sure you can see the difference between the two photos after it was dusted and cleaned. So let the repair begins.

how to fix welding machine

Since I am dealing with amp setting of the machine I headed directly to that area and there is usually a transistor SS8050 that is connected to the amp knob.

Unfortunately the transistor was fine but the problem it was not getting the right voltage so more checking has to be done in that area.

repair and fix welding machine

I believe and almost sure that the marked area is where the fault is located so I started checking components in that area and soon enough the fault has been found.

repairing welding mahcine

These two resistors with the value of 33k and 2300 ohms were found open and were replaced. Checking further I found these two Zenners diode shorted as well. I used my soldering iron to take out the Zenners next to these resistors they both fell apart. The part number is CBV25T and since I have the same donor board in the shop I replaced these two right away.

how  to fix a broken welding machine

Once these four components were replaced, I put the machine back together and hoped for the best.

delta mma200 repair

The photo is out of focus but it is clear enough to see that the machine is working again. I took it to my brother next door and he did some welding on it and this time it was up and running according to specs.

It is the first time I encounter such fault but it was a success and new experience gained in this kind of repair.

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.

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Note: You can check his previous article on A Full HD Car DVR Does Not Power Up For An Obvious Reason Repaired




  1. Parasuraman S

    January 20, 2024 at 11:05 am

    Many thanks for sharing! It is a good fix! Very professional! Well done!

    • Waleed Rishmawi

      January 20, 2024 at 3:47 pm

      Parasuraman: thanks man. have a blessed day

  2. Tayo

    January 20, 2024 at 7:05 pm

    Good knowledge share Waleed. To be honest I would not have had a clue where to start looking ... but if I ever come across a similar problem I do now!

    • Waleed Rishmawi

      January 20, 2024 at 9:48 pm

      Tayo: it is my first time I encountered such an issue so never give up on learning new things here and there. Have a blessed day.

      • Sebastian Mendoza

        January 31, 2024 at 11:54 pm

        Excellent job, my friend!

        Last year, I started fixing these kinds of machines, and your blogs have been very helpful. I've been learning a lot from you, thanks for sharing your repairs!

        I'm here today because I'm interested in learning about the design of the current limiter you use. While I've only tripped a breaker a few times, I'd like to avoid it in the future with the current limiter you've been using.

        Thank you very much for your blog! Greetings from Latin America!!!

  3. Albert van Bemmelen

    January 20, 2024 at 7:19 pm

    By now you have must have collected so much data about doing these repairs that it makes you unique in the world of Welding machine repairs!

    • Waleed Rishmawi

      January 20, 2024 at 9:51 pm

      Albert: thank you for your nice and kind comments. I am collecting data and keeping a record of it and use it as reference for welding machines repair. Have a blessed day

  4. Yogesh Panchal

    January 20, 2024 at 9:23 pm

    Good fix! Waleed

    • Waleed Rishmawi

      January 23, 2024 at 2:10 pm

      Yogesh: thanks man. have a blessed day

  5. Bernie Scott

    January 20, 2024 at 10:33 pm

    very well done.......I commend you for your ability to repair electronic equipment...I always try to tackle things I have not seen before and believe me, the experience and gratitude upon completion of a successful repair is very rewarding......keep up the good work......

    • Waleed Rishmawi

      January 23, 2024 at 2:11 pm

      Bernie: thanks man. yes it is. keep up the good work and have a blessed day


    January 22, 2024 at 3:04 pm

    what voltage were the zener diodes ?

  7. Waleed Rishmawi

    January 25, 2024 at 5:21 am

    I think 25 volts. Have a blessed day


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