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.
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You may check on his previous article on Beware Of These Fake PWM ICS