Saved Another Computer SMPS From Dump
This iBall Computer SMPS model LPS223-400 belonged to the hospital where I work. It was brought to me dead. As my IT colleague had already opened the unit and cleaned it up thoroughly, it saved me the work. I found one transistor in primary short and ESRs of almost all the caps out of the ranges. So took this up for replacement one by one.
Here are pictures of couple of these, which show the value read by SMD capacitor tester (Not ESR readings):
After replacing all the electrolytic capacitors, I did a thorough dry solder patch up of the board and cleaned it up thoroughly using IPA. Then when I checked, the output of 5V was coming, but getting loaded and dropped. I suspected the PWM controllers.
So fit two IC sockets after removing the two ICs. Put two ICs from another salvaged SMPS. Then applied power with a load of 12V, 25W bulb. Voltage was steady.
So fixed the board back to its case and connected my ATX SMPS tester and found every output ok:
Do I have to say that the mission was accomplished with satisfaction getting added to the bag?
Here is the picture of the defective components:
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 Dry Solder And Defective Capacitors Found In Philips AZ380/94
Albert van Bemmelen
February 12, 2022 at 10:06 pm
If we get those old smps units fixed and good to go is fun, although you are obviously great in doing that better than most of us. I recently ordered a brandnew 700 Watt smps desktop unit for less than 30 Euro's including shipping to make sure I have a good spare replacement unit just in case I can't repair my old one.
Anwar Y Shiekh
February 12, 2022 at 11:15 pm
I would be worried about using a 30 Euro supply.
February 13, 2022 at 2:16 pm
February 12, 2022 at 11:57 pm
It is always a thrill to repair one rather than going for a new one. Many thanks for your comments!
February 13, 2022 at 9:45 am
I like your articles. I need more technical repair article on Inverter AC circuit. Could you post the same.
February 13, 2022 at 2:17 pm
I do not handle AC inverter curcuits. Shall share as and when one comes. Many thanks!
February 13, 2022 at 12:39 pm
Thank you so much for sharing.
February 13, 2022 at 2:18 pm
February 13, 2022 at 8:06 pm
Thanks for sharing this repair. You are the expert on these things obviously and someday I will have the chance to work on such power supplies; they seem complicated
February 14, 2022 at 4:58 pm
SMPS service was a nightmare for me until I read Jestine Yong's Book on SMPS repair! Afterwards, it remained an interesting challenge! Many thanks for your comments!
February 14, 2022 at 2:53 pm
Great sharing.. thanks
February 15, 2022 at 4:18 pm
February 15, 2022 at 12:09 am
Good Job! Sir,
I have purchased few Non working SMPS from junk shop.repaired most of them are just open Fuse and rest of with burnt out PCB inside.Salvaged parts from those SMPS.
Now i can use this SMPS as Bench power,Because this power rails provides high amps in 12V, 5V & 3.3V which we can use for testing & troubleshooting process.
February 15, 2022 at 4:20 pm
Yes, it is very useful. But variable power supply is what serves the purpose! Many thanks for your comments and inputs!