Saving Computer SMPS Part – 8
Case (1) FOXIN-FPS500C: This was brought to me with the complaint that the fan broke while in use and it stopped working. After doing the secondary cleaning work inside, I looked for any bulgy capacitor or defective components other than the fan and could find only one 12 Ohm resistor charred in the secondary. I replaced the resistor and the fan, upon which the SMPS was back to work again:
Case (2) IBALL-LPE223-400:
This was brought to me in dead condition.
On inspection, I found capacitors bulged and NTC and another AC cap connected between the hot ground and body cracked.
As ring tests showed healthy, I proceeded to replace the burnt components and also all the electrolytic capacitors since the values had dropped drastically. Then did a thorough retouch of the board happily singing like a nightingale and swimming in imagination like a swan! After this work, took snaps like a man who scaled the mountain. Connected load and applied power to see that the 5V standby got on and the fan just turned a bit and stopped and all other voltage indications got off within a few seconds. Something was amiss and so I discharged the tank caps and looked for the trouble maker. Combed the entire area! Replaced the Opto, two TL431s, removed the main IC and looked for any shorts anywhere. Nothing could be found! I looked for the datasheet of this IC and tried to get a replacement and that was not available. Looked for an equivalent from my salvaged boards. Though I found the pins were matching, it did not work at all. I had soldered an IC socket for the purpose of such tests. In the meanwhile, using the lens I looked for any shorts on the board a few times. Then kept this SMPS away and took up other jobs.
After a week or so, took it up, put the IC back and switched on expecting that some angel would have set it right while in storage! (LOL) But something inside me was telling that this could only be due to some man-made shorts. Repeated probing for such a possibility did not yield any positive result, mainly because of my over-confidence and taking things for granted. Once again kept the SMPS away and proceeded with other works. Once again took it up after I was successful in setting right a complicated SMPS repair work. Then, found the following man-made short on the board:
Then removed the short, replaced the IC and TL431 and fan and applied power to cry ‘hurray’ after seeing the result:
So, unlike the previous cases, this happened to be a complicated repair, made by my sheer negligence and over-confidence! Learnt a lesson not to be so carefree and to use a soldering iron with sharp tips instead of the lancer type.
Anyhow, double satisfactions got collected as both the jobs were for the hospital and a free service!
This article was prepared for you by Parasuraman Subramanian from India. He is 74 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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Albert van Bemmelen
April 6, 2024 at 5:10 pm
Nice repair story Pararasuraman! YOU and over-confidence? There is no such thing! (LOL!)
I guess that the TL431 and other parts that were discarded in the process are still fine to be used after all.
Parasuraman S
April 6, 2024 at 10:24 pm
Many, many thanks for your encouraging comments!
Paris Azis
April 6, 2024 at 5:12 pm
The magic starts with that:”Then kept this SMPS away”...This seems to be the unique problem solver in such cases! One hour max troubleshooting. If the problem is still there, then the device stays on a place on the bench, until next day morning, where the mind is clear and the coffee is inspiring the most! No way for the trouble to escape! In most cases it’s solved within the first ten minutes. This was and still is my method for years now. Every time I was stubborn to solve the problem spending hours, the problem was “in front of my nose”, smiling ironically at me, but I couldn’t see it, being myself blatantly defeated!!...
My greetings Parasuraman! You certainly deserve a nice and tasty coffee!
Parasuraman S
April 6, 2024 at 10:26 pm
Vow! Those are very valuable and encouraging comments! Many thanks!
Tayo
April 7, 2024 at 6:38 am
If I subscribed to this methodology... I would never get anything done! Maybe it's just me and my inexperience but Im just getting warmed up after 1 hour of useless probing and guessing! haha.
Parasuraman S
April 7, 2024 at 2:45 pm
Ha! Ha! Keep trying until you succeed! All the best!
Yogesh Panchal
April 6, 2024 at 6:16 pm
Good Job! Sir,
i also faced this type of problem because when we troubleshoot consuming more time our maid get stuck in particular pattern,better day is another day when your memory cache is Refreshed.
Parasuraman S
April 6, 2024 at 10:27 pm
Yes, dear! Our mind gets blocked! Thanks for your comments!
Waleed Rishmawi
April 6, 2024 at 10:43 pm
I like your story but where that short come from? Glad you were able to get them fixed. Have a blessed day
Parasuraman S
April 7, 2024 at 2:46 pm
Many thanks for your comments!
Yogesh Panchal
April 7, 2024 at 12:10 am
Good Job! Sir,
i also faced this type of problem because when we troubleshoot consuming more time our mind get stuck in particular pattern,better day is another day when your memory cache is Refreshed.
Parasuraman S
April 7, 2024 at 2:47 pm
Many thanks for your comments!
Anwar Yunas Shiekh
April 7, 2024 at 1:07 am
We all get over confident; how else coud we survive in this complicated world.
Parasuraman S
April 7, 2024 at 2:47 pm
Yes, true! Many thanks!
Imoudu.O
April 7, 2024 at 4:34 am
Cool brain/mind is always active.Thanks for sharing sir
Parasuraman S
April 7, 2024 at 2:47 pm
Yes, very true! Many thanks, dear!
Tayo
April 7, 2024 at 6:44 am
Well played Parasuraman. Those man-made bridges are the worst. I am guilty of being in a haste and leaving more than a few bridges on the bottom of boards. Good fresh flux and very thin high quality solder flux (0.8mm) helps a lot.
Parasuraman S
April 7, 2024 at 2:48 pm
Yes, it happens! Many thanks!
Rodrick Makanga
April 7, 2024 at 4:22 pm
Congratulations for happy ending
Parasuraman S
April 8, 2024 at 10:56 pm
Many thanks, dear!