Burst TNY280PN IC Found In An Opthalmic Eye Vision Drum SMPS That Got Charred
This SMPS was brought to me with the complaint that it went dead with a loud bang. The top of the TNY280PN got tossed away by the impact and was lying loose within its case. Luckily the number was intact. Let us have a look at the damages that had taken place; first when the defective components were in place and then the condition of the PCB underneath, as the pictures would speak better than words: (One 10uF/450 cap had burst spewing the “HOT LAVA” around!)
Now, the next stage, which is after cleaning the board, collecting all new components for replacement, then fixing them and retouching the board thoroughly from one end to another:
Before populating the PCB with new components, a ring test was done on the SMPS transformer which showed a healthy reading. This is a very important step as otherwise our efforts would become futile.
Then checked all the remaining components on the board thoroughly. The optocoupler was checked touching the pins 1 & 2 with an analogue multimeter in X1 range and checking the ohms reading at pins 3 & 4 in a DMM, which showed around 20 Ohms. Then checked the TL431 with DMM in diode mode. Rest of the diodes on the board were checked with Analogue Multimeter in X1 mode as well as DMM in diode mode. Jestine Yong, a world famous expert in teaching, has mentioned the need of using Analogue Multimeter in X1 range in his popular SMPS repair book. In fact, I do not mind repeating yen number of times that my inspiration and inclination to take up SMPS repair work got registered only after reading through it. Even a minor leakage of the diode might go unnoticed in DMM reading. But Analogue would show you that either in X1 range or X10 range. Even transistors are being checked by me regularly like this.
Many of you by now would have asked this question in the mind ‘Ok, buddy! What is the result?’ Here is the answer for that: (Also given side by side is the image of the defective components and the board with new components)
I always cherish in repairing SMPS and the immense satisfaction derived by this restoration had no difficulty in getting an entry into the (now world famous) collection bag!
Here is one concluding picture that showed the display working, shared by the customer later: (This sits on the wall on top of the patient under test, reflecting it to a mirror opposite at a distance. I am sure many of you would have already seen such set up. In certain places, there is yet another illuminated display inter connected to this main unit.)
This article was prepared for you by Parasuraman Subramanian from India. He is 76 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 Two Simple Jobs On LED TV Servicing – SAMSUNG UA43N5005AK & IMPEX-GRANDE 32 SMART
(1)Dislikes
(0)
