A Serious Mistake In 12 Volts Power Supply Repaired
A friend of mine and a fashion store owner brought me three power supplies for repair. He said the electrician tried to fix something in his store but instead he damaged these three LED power supplies there.
As seen in the photo, the three power supplies were dead and needed repair but I only picked one power supply to write the article about.
The first thing that I saw when I took the metal shield off was this blown fuse and with the fuse blown,
I am sure there are other components like the bridge rectifier and other parts are damaged as well.
The first thing that I came across was the main capacitor and as seen in the photo, it has a short across the negative and the positive terminals of that capacitor.
The bridge rectifier was also damaged along with two Mosfets (HGTG20N60C3) on the secondary side of the power supply.
Click here or the above photo to access HGTG20N60C3 datasheet
Once these parts were replaced and installed in this power supply,
I connected it through a current limiter device and as seen in the photo, the green LED light came and that is a very good sign.
I did a quick test to make sure the 12 DC volts are there and the photo confirms that loud and clean.
I put the metal shield back on and called the customer but the customer suggested that I go to his store and connect these power supplies to make sure all are working within their specifications.
A job well done is what I heard from the customer and that put a smile on my face that there are still people out there appreciate what we do in the repair field.
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 Could Hear Relay Click Sound But No Continuity…..
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Anwar Y Shiekh
December 3, 2021 at 10:07 pm
Now I am confused, what could the electrician have done that damaged these?
Tayo
December 4, 2021 at 7:44 am
I too am wondering what the 'serious mistake' the prior electrician made here. I cant think of anything they could have done which would have taken out 3 power supplies on a properly installed circuit. Only a lightning strike would do something that destructive and that that would hardly be the electrician's fault unless he removed the main ground/sink entirely.
Waleed Rishmawi
December 4, 2021 at 1:36 pm
Tayo: not sure what the electrican did but the damage was done. according to the customer, everything was up and running till the electrican came and few minutes later, the damage happened. there was no lightning strike. have a blessed day
Waleed Rishmawi
December 4, 2021 at 1:32 pm
Anwar: according to the customer, the electrician came to do something in his shop and then did something to cause the earth leakage key to trip and this fault came to me..not sure what went wrong but the damage was done
Imoudu Onwumah
December 4, 2021 at 12:37 am
Good job, a smiling customer goes a long way!!
Waleed Rishmawi
December 4, 2021 at 1:37 pm
Imoudu: thanks man, yes the customer was happy beause these transformars are expensive. have a blessed day
amr hamza
December 4, 2021 at 12:45 am
good job
Waleed Rishmawi
December 4, 2021 at 1:37 pm
Amr: thanks man. have a blessed day
Albert van Bemmelen
December 4, 2021 at 1:16 am
As you wrote: a blown fuse and with the fuse blown, a defect that must be defect of course (lol).
I wonder whatever happened that killed all those components in 3 of these Led power units? Probably because of bad shorting 680uF 250V e-caps that started this?
Waleed Rishmawi
December 4, 2021 at 1:40 pm
Albert: an electrician was working in the customer's shop doing some kind of work not sure what it was and the damage was done few minutes after the electronic started to work ( according to the customer). have a blessed day
Dany Verhamme
December 4, 2021 at 9:07 pm
Albert, has to do with overvoltage caused by earthfault on certain main power supply (example IT)
Phase voltage becomes Line voltage and the EF breaker trips and the 3 power supplies are all damaged at the same time
Paul
December 4, 2021 at 1:44 am
Hi,
Please explain why you need high voltage transistor HGTG20N60C3 on the secondary side of the power supply.
Waleed Rishmawi
December 4, 2021 at 1:44 pm
Paul: these transformers are usually used to power up security cameras and it needs a high amp rate transformers so the electrican suggested these transformarts to power up LED lights in his shop and they did. have a blessed day
Lynn Blakely
December 4, 2021 at 1:47 am
Good Job Waleed we like the way you visually inspect and then confirm the parts that are affected. Those are good lessons for those without experience, and or training.
Waleed Rishmawi
December 4, 2021 at 1:45 pm
Lynn: thanks man. I appreciate your comment. have a blessed day
Tony Repair kenya
December 4, 2021 at 3:51 am
I wish upcoming techies learnt the current limiter trick it saves a lot of troubleshooting time. Great article Mr Waleed.
Waleed Rishmawi
December 6, 2021 at 2:54 pm
Tony: thanks man. have a blessed day
Teofilo M. Sagabaen
December 4, 2021 at 5:31 am
Very informative!
Waleed Rishmawi
December 4, 2021 at 1:49 pm
Teofilo: thanks man. have a blessed day
Carlo Alberto Birocco
December 4, 2021 at 6:55 am
Poor quality of electrolytic capacitors is the "curse" of power supplies ... But You had a smart approach, because this capacitors not seems bulged as usual. Well done!
Waleed Rishmawi
December 4, 2021 at 1:55 pm
Carlo: actually the capacitors are good quality ones but they went through a bad power surge caused one to be bulged, bridge recetifier to be shorted along with two mosfets to short out. it was a mess but it was repaired to the satisfication of the customer. have a blessed day
Parasuraman S
December 4, 2021 at 3:26 pm
The ultimate fix accomplished by you as usual! Customers are really lucky to have you at their disposal!
Waleed Rishmawi
December 4, 2021 at 6:34 pm
Parasuraman: thanks man for your kind words. I appreciate it very much. have a blessed day
Mark
December 4, 2021 at 4:15 pm
Well done Waleed.
Waleed Rishmawi
December 4, 2021 at 6:35 pm
Mark: thanks man. have a blessed day
Yogesh Panchal
December 7, 2021 at 4:10 pm
Waleed,
Now a days these type of CCTV SMPS are comes with PPTC resettable fuse inside which protect against over current faults & once you find the culprit and isolate/solve the problem the fuse will reset automatically.may be Electrician must have connected 12V O/p wires to mains by mistake.
yes of course our work is to make it in order to work and you did it.
Anwar Y Shiekh
December 7, 2021 at 11:30 pm
Now in the USA with split phase I could imagine a broken neutral can take a 110V circuit to 220V, but as far as I know you don't use such a system out there
Humberto
January 14, 2022 at 11:42 pm
Thanks for sharing this good repair.