Dry Solder And Dropped Value Of Caps Found In ATX SMPS
In this article the new comers can learn (1) One of the major causes of SMPS switching not taking place (2) Why a total dry solder patch up is necessary in this type of power supplies and (3) Why a load has to be given before final test
This ATX SMPS belongs to the hospital where I work. It was brought to me with the complaint that it was not taking the load and gets switched off.
I opened the cover and my colleague helped me clean the inside thoroughly. I checked for the trouble maker in the board and found a lot of dry solders and ‘ESR out of range caps.’ When I checked the tank capacitors the value had dropped drastically:
So, replaced all the electrolytic capacitors, thoroughly combed for any defective components in primary and secondary and did a thorough patch up of dry solders on the board.
Then cleaned the board very well.
Then powered it up, giving a load of 12V/25W automobile bulb. It was found working very well.
So, fit the board back to its case and once again tested it with power supply tester and found all output voltages normal.
Here is a picture of the caps replaced:
(1) One of the major causes of the SMPS not switching on, is electrolytic capacitors in its primary becoming weak. Testing is possible only by removing and checking its value (2) It is absolutely necessary to do retouch of all the points on the board and check all other components thoroughly before switching on the unit to avoid further failures (3) Giving a load to the unit is necessary for checking stability of its working.
Mission accomplished with addition of satisfaction getting collected into its storage.
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.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous article on Beware Of These Fake PWM ICS
(62)Dislikes
(0)
18 Comments
Leave a Reply
Mark
February 26, 2022 at 5:00 pm
Another great repair Parasuraman!
Parasuraman S
February 26, 2022 at 11:11 pm
Many thanks!
Albert van Bemmelen
February 26, 2022 at 5:44 pm
Another very learnful and pleasant to read instructual from our Indian Master!
PS: Noticed the nice about 20 euro handheld MS8910 smd tester you used in the article. I have the Mastech MS8911 that probably also uses a larger 3V CR2450 lithium battery.
Parasuraman S
February 26, 2022 at 11:12 pm
Many thanks for your share and encouragement, dear!
Anwar Y Shiekh
February 26, 2022 at 9:16 pm
What a great idea to do load testing with a car light bulb; a worn-out headlamp bulb also works as normally only one filament is broken.
Parasuraman S
February 26, 2022 at 11:13 pm
Yes, dear, one filament is blown in that light, which I kept aside for these type of tests! Many thanks!
Babu M S
February 26, 2022 at 11:48 pm
I am the new comer for the smps repair work. Your good instruction will use full to me carry out repair works. Thank you very much for sharing.
Parasuraman S
February 27, 2022 at 5:13 pm
Welcome and all the very best! Many thanks! (I would suggest you go for Jestine Yong's book on SMPS repair! It is one of the best!)
Yogesh Panchal
February 27, 2022 at 12:32 am
Good Fix! Sir,
Parasuraman S
February 27, 2022 at 5:13 pm
Many thanks!
ANIL KUMAR V K
February 27, 2022 at 12:37 am
Excellent work sir
Parasuraman S
February 27, 2022 at 5:14 pm
Many thanks!
Lynn Blakely
February 27, 2022 at 2:09 am
Sir Parasuraman: Another item happily goes into the satisfaction bag. Replacing all those capacitors is to assure longevity to the life of the power supply, and stops callbacks.
Parasuraman S
February 27, 2022 at 5:15 pm
Yes, dear! You are right! Many thanks for your comments!
jai Etwaroo
February 27, 2022 at 12:07 pm
Good work Parasuraman, I have been following some of your past repairs.
Parasuraman S
February 27, 2022 at 5:15 pm
Many thanks!
Anwar Y Shiekh
March 3, 2022 at 5:20 am
I have a USB 3 hub that also suffered dry solder joints; lots of flux and a reflow seems to help.
Parasuraman S
March 5, 2022 at 7:00 am
Yes, a reflow might help! Many thanks!