Open SMPS Transformer Hand-Wound In Mobile Charger TC-70
For a change, this time it was my own device that became defective. My mobile charger conked off one day and I kept it aside for investigation for a later day.
Recently, I just opened the case and checked as to what went wrong. The fuse (a low ohm resistor) was intact. I did not find any pot belly cap either. When I used the ring tester, the LEDs did not light up. Though I checked up all the components in the primary and secondary, there were no defectives. At-first I was baffled.
Then by a sheer chance, I used my multimeter to check the primary of the transformer and was surprised to note that it was open! First I thought it could be some dry solder on the leg. So, I removed the transformer.
After doing one more checking to be doubly sure, I peeled the outer tape and gently looked into for any burnt end or fungi attacked leads. There were none. I became curious. I shook the Ferrite Formers by inserting plastic screw drivers and after nudging several times, it became lose. Then I sprayed IPA on the bonds, and finally it got released. Then, I made note of the winding direction and started removing the coil one by one. There were totally four windings. After removing the third winding, I saw the place where there was a fungi formation and the wire was eaten away there. This was on the fourth winding.
As there was only a dot which was cut, I soldered both ends and covered it with tape to provide insulation. Then wound the coils one by one by hand, making it as close as possible and following the order in which it was wound.
Unfortunately, in my excitement I forgot to click the stages. After rewinding and fixing the formers, the transformer looked in good shape.
Then fit it in the board and tested it to find the output voltage giving a pleasant surprise and experience!
Mission accomplished adding intense satisfaction to the collections.
Following are the pictures of Switching IC and battery charge control IC:
This article was prepared for you by Parasuraman Subramanian from India. He is 72 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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You may check on his previous article on Rusted And Corroded Crystal Oscillators Found In Cambridge Audio AZUR-540C
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17 Comments
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Andrew F. Ali
February 24, 2023 at 9:19 am
I clicked 1 dislike in error. I meant to clike LIKE.
Please accept my apologies.
Great job!!
Parasuraman S
February 24, 2023 at 3:17 pm
Its ok! I liked your dislike too! (LOL) Many thanks for your comments!
Anwar Shiekh
February 24, 2023 at 10:32 am
Beautiful work
Parasuraman S
February 24, 2023 at 3:17 pm
Many thanks for your comments!
Albert van Bemmelen
February 24, 2023 at 1:47 pm
Another very well carried out repair that I normally would have skipped!
Parasuraman S
February 24, 2023 at 3:18 pm
Many thanks for your comments and encouragement!
Arunkant L Pandit
February 24, 2023 at 2:50 pm
Sir,
Quite difficult task carried out successfully. Well described article. Thanks for sharing.
Parasuraman S
February 24, 2023 at 8:49 pm
Many thanks for your comments!
Simphiwe
March 19, 2023 at 6:58 am
Wonderful stuff,i'm very scared to dismantle wound devices like trafos & coils..i admire your skill& perseverence..
Waleed Rishmawi
February 24, 2023 at 6:22 pm
great work my friend. thanks for sharing and have a blessed day
Parasuraman S
February 24, 2023 at 8:50 pm
Many thanks for your comments, dear friend!
Henrique J. G. Ulbrich
February 24, 2023 at 8:12 pm
Great job, Parasuraman. And different in two aspects:
1) You didn´t find any capacitor to change. It´s rare in your reports. Perhaps you are sad about....
2) It was a different, unconventional repair, in that you used a lot of patience to deal with transformer wounds.
Many thanks for sharing this remarkable experience.
Parasuraman S
February 24, 2023 at 8:51 pm
HA! HA! Many thanks for your hilarious comments!
Yogesh Panchal
February 27, 2023 at 8:42 pm
Good Job! Sir
and very much agreed to Albert's comment.
Parasuraman S
March 1, 2023 at 12:23 am
Many thanks for your comments!
Mahmoud
March 1, 2023 at 9:06 pm
many thanks to you...
for sharing your repair steps it was a great job well done
Parasuraman S
March 2, 2023 at 12:23 pm
Many thanks for your comments and encouragement too!