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