One Zener Diode Found Cracked And Another Shorted In CCTV SMPS
This 12V SMPS of a CCTV Camera was given to me by my technician friend, stating that it was reported to be dead. I brought it home and subjected it to thorough cleaning inside and outside. The cover was already open and was not having its screws.
As I noticed a lot of dry solder on the board, I cleaned it first and carried out retouching all the solder joints fresh and cleaned it again.
Applied power and noticed that there was no output.
So, disconnected and discharged the tank capacitors. Carried out ESR checking of caps and Ring testing of Transformer both of which got passed. Then I checked each and every component on the board, first of which was all diodes. While checking, I noticed that one 13V Zener was short and another one next to it was found cracked.
The crack was not easily visible, and chanced to see it only when I pressed the probes at both ends for checking. Unfortunately, the value was on the two cracked pieces and I could not make it out. So, I used Fevibond and stuck the two pieces together exactly how it was and then read the value, it was 6V2 Zener.
Replaced both Zener diodes. Checked rest of the components and could not find anything else faulty. So, powered the SMPS through a series bulb like before. It worked very well, with its SMPS Fan whirring smoothly:
So, reassembled the board and rechecked it:
Another interesting troubleshooting completed satisfactorily, qualifying itself to jump into the bag!
This article was prepared for you by Parasuraman Subramanian from India. He is 69 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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