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Crude Drawing To Find Out Burnt Components Part Number
This Brite Lite Adapter belongs to one of my friends, who brought it to me knowing my craze to restore any electronic gadget, irrespective of its cost. The complaint was ‘dead’!
Opening is possible by just peeling away the silver sticker at the bottom, and removing one holding screw.
On visual inspection, found that one transistor had burst, and on further cold tests, a few other components were too found defective. One 2N3904 was burst, another MJE13003 short, opto-coupler short, Diode short, 2 SMD resistors open, green capacitor burnt, and another changed value. All these were in the primary. On the secondary, one diode was short! So, this was a massive heart attack!
Whenever we see such mass failure, we have to check whether the SMPS Transformer is ok. I checked it with Ring Tester and found it to be ok. But in order to make sure, I removed the MJE13003 and connected a Universal Module, after replacing the diode in the secondary side. The LED lit indicating that all was well in the secondary side.
Removed them one by one, noting down the reference number from the PCB and the corresponding component.
While replacing the 13003 transistors, we need to be careful, as the order of pins might not be same, as you can see from the below pictures:
I also drew one circuit diagram, which could help me in future (crude drawing!), from another working adapter that I use with my torch.
The circuits were identical. That is how I knew that the burnt transistor was 2N3904 and the value of burnt SMD resistor!
Then I drilled holes (using a special hand-drill) in order to replace the resistors, as the SMD was not available. I had to use three resistors in series to arrive at the value of 360 Ohms!
After rechecking that everything was ok, I powered it through the Serial Bulb.
Assembled it back and left it on connecting the load and found it to be working fine.
Finally, the Adapter was saved from dump, though this might have made a hump on my back!
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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