Six Power Mosfets Shorted and…..
this Link.A severe damaged welding machine repaired. Model: Zika I-200
My cousin brought his machine for repair. I have seen this machine before but this time the damage was very severe. Take a look.
It was completely dead. My cousin mentioned something about a loud exploding noise heard the moment he plugged it into the wall power socket. I never heard of such cause of fault.
He also explained that the power switch was on the moment he plugged the power cord into the wall socket. Very interesting.
The moment I took the metal cover off, I saw this damage on one side of the Mosfets. I could see the black burn there and that is not a good sign at all.
It is always better to take the part under test off board for better testing result but in this case I just wanted to have an idea of what I am dealing with. At this moment I was getting short reading on all the Mosfets but I know for sure not all of them were shorted out.
I tested all the Mosfets off board and I found that six of these parts are shorted out.
Every pin on these Mosfets was shorted out which means there are other parts that are already damaged. The part number is 23N50E which I have plenty of in my shop.
Click above to go into the 23N50E Datasheet website
These were the blown parts bunt and blown to pieces. From my experience in these machines, the diodes are FR104 and the resistor either 2K or 100K Ohms depending on the model.
Click above to FR104 Datasheet Website
These are the replaced part on this machine and it was time to test it out and see the outcome of this severe repair.
That is not what I had in mind. This voltage is too low for the welding to take place in this kind of machines. I was getting this reading when positive probe on the positive output and negative on negative output of the machine but when I reverse polarities, I get 75 but in minus.
That was a very strange reading indicating a bad main board and again, that is not a good sign at all.
That is the main board located on the top board of the welding machine. I was looking for faulty parts on that board and guess what? I found two Zenner diodes that were shorted out keeping in mind that the Mosfets I replaced is connected directly to this board. The faulty Zenner diodes found here were 3.1 volts. The closest Zenner value to this that I have in my shop was 3.9. I decided to replace that and see what happens.
This is what I had in mind and as it went through tough testing by my brother the welder next door, I could say with confident, it is an up and running welding machine.
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://jestineyong.com/a-dead-reading-book-toy-was-brought-back-to-life/
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Lynn Blakely
May 6, 2020 at 10:30 pm
Good Job, You are always very detailed and complete in checking all the suspected components. Excellent detailed explanation of repair.
Waleed Rishmawi
May 7, 2020 at 4:02 pm
Lynn: thanks. I appreciate your positive encouraging comments. have a blessed day
Albert van Bemmelen
May 6, 2020 at 11:25 pm
Replacing 3V1 zeners by 3V9 types seems not a good thing to do. And in cases where 6 of those big Mosfet are gone and other parts are damaged too, it is questionable if the owner is maybe mistreating his device. With the risk that this machine maybe will come back for another repair soon?
Waleed Rishmawi
May 7, 2020 at 8:35 am
Albert: might be the case but so far it has not come back for repair. This was done about one or two months ago. Have a blessed day my friend.
babu ms
May 7, 2020 at 12:28 am
Excellent job.I have learned lot from posting of your articles and excepting many more please. Thanking you.
Waleed Rishmawi
May 7, 2020 at 4:03 pm
babu: thanks. I am glad you are learning a lot from the articles. I am alway encouraged to hear that. thanks for sharing. have a blessed day
Parasuraman S
May 7, 2020 at 11:54 am
Another 'welding' service well done! But I dislike replacement of 3.1 with 3.9V Zener, as rightly mentioned by Albert Van Bemmelen. It is better to put the correct value, as company designs are based on a lot of research and development.
Waleed Rishmawi
May 7, 2020 at 4:06 pm
Parasuraman: thanks man. yes, the right value should always be the replacement but in my case, we were under lock down and none of the stores were open to buy them so I replaced with what I have. so far it is going great and no complaints.
N K Ahuja
May 7, 2020 at 2:11 pm
Replacing 3.1v Zener with 3.9v Zener is not done. If the machine is being serviced in a workshop it is not difficult to get Zener of correct rating. By posting this article you are giving a wrong mesasge. The machine may work for some time and again may become faulty because of use of wrong value. The correct method is to remove the root cause and use same or equivalent parts as recommended by company or as per data sheets.
Waleed Rishmawi
May 7, 2020 at 4:10 pm
N K Ahuja: yes, I understand your concern but I could not get the right zenner value due to the Virus lock down, so I replaced it with what I have. it has been over 45 days now and it is still working like a charm. keeping in mind, I had another machine of the same design but different brand name that uses 3.9 zenner value. so no complaints so far and the machine is still up and running. have a blessed day.
nkokana
May 7, 2020 at 5:16 pm
hey friends.I have a laptop here which is HP that does not show on screen.the screen is blank.when i connect it to the external monitor the picture is there.what could be the problem here. i cleaned the RAM and HDD connectors but in vein. what could be the problem here..can it be the LCD panel its self or the mother board
Albert van Bemmelen
May 8, 2020 at 12:40 pm
That is a good question that can have many answers my friend. It can be the screen backlight, the bios chip, a defect mosfet, a defect video chip, a bad video cable and so on. Without correctly diagnosing the mainboard and other hardware by some testing and measuring, advisably with the right schematics/service manual at hand, it is sadly impossible to tell in this short reply nkokana.
Albert van Bemmelen
May 8, 2020 at 12:45 pm
But since you wrote that the external video signal is okay you can much likely rule out a bad videochip, and a bad Bios! Good luck!
Alphonsus Lim
May 8, 2020 at 11:17 am
A great job completed Waleed Rishmawi I like reading your article very direct and precise.
Thank you very much.
Waleed Rishmawi
May 9, 2020 at 5:27 pm
Alphonsus: thank you very much. have a blessed day
Albert van Bemmelen
May 8, 2020 at 12:52 pm
However... once my brother had a corrupted Bios on his quad-core desktop computer mainboard that caused the Ethernet/LAN connection to fail. It looked as if the LAN driver was refusing to work, but after all it was a bad Bios chip. After it was replaced by a new 8 sop Eeprom chip everything worked splendedly! That particular repair was also uploaded in one of my older mainboard Bios diagnose articles on Jestine's Blog.
stanley
May 19, 2020 at 2:10 pm
waleed l also discovered that replacing the 3.1 with 3.9 might be the way to go.sometimes manufacfurers make these mistakes.was thinking why we replace a cap of say 470uf25v with 1000uf35v.are catching my drift
balkrushna Kadam
October 28, 2021 at 1:17 am
I have similar welding machine, MOSFET driver board has a capacitor 224j100, i want to know substitute of this capacitor which I can replace it with.