40 Inch Samsung LED Television Hit By Power Surge Now Repaired
I received a phone call from a caller who was not on my phone book and since I have my business line all over on my webpages and other social handles I always pick the call without paying much attention who is calling.
The caller introduced himself that he got my number from an Uber friend that I do electronics repairs.
I was on my way out of the shop to town to buy spares for the television which was already on my workbench.
Since the caller was around my place, I figured out that since the television has succumbed to power surge according to the information he gave and again power surge damage is usually catastrophic and therefore easy to get culprit since most component failed can be picked using naked eyes.
I decided to wait for him to bring the television to the shop so that I can check the failed components and go check them in town one trip.
Within 10 minutes the client was in my shop. I applied the power as I usually do the initial tests and the television was dead completely, even the power On led was off.
Before opening I was very sure the fuse was gone, I opened the television and this is what I saw.
Like I said you don’t need to use a meter to confirm the above components have failed and therefore should be added to the replacement list. I pulled my meter and headed straight to the main fuse, to my surprise the fuse was okay. I tested across the inputs of the bridge diode looking for shorts and I found its okay also. I check each transistor on the power supply and found them they were all okay.
Then I decided to go to the shop to buy the part but one thing was sure is that getting the line filter(inductor) which was burnt in the market is next to impossible and therefore I usually buy them from other technicians who keep junks of all kinds.
I visited the yard and I was not lucky, while figuring out what next I remembered I had Samsung TV with screen cracked and has stayed in my shop over one year, I decided to go back with other parts which are readily available in town.
Back in the shop, I checked on the junk TV and I was lucky to get the missing part. I installed it together with the two capacitors and applied the power via the series current limiter bulb and the bulb confirmed to me that there is no short on the board.
I decided to test across the output of the power supply and I got voltages and very stable, this put a smile on my face. As I celebrated the easy fix, I decided to question this scenario, how can a brand like Samsung not trigger the fuse to open until the Line filter (inductor) almost went into flames?
Then I remembered my basic electronic something about inductors. See the diagram below.
Basically an inductor function as a filter, which allows low frequency to pass but make it very hard for the high frequencies to pass.
Looking at the circuit above you can see that an inductor is in series with the power line, this means it will allow low frequency of the power supply (50hz to 100hz) and make it very hard for the high radio frequencies to pass.
Although the coils were badly burnt kindly note that the two coils are separated with a small gap between the live and neutral and hence at no point did the two path short and that explain why the fuse did not blow.
Eventually the coil became open circuit and cut the main power from moving forward and hence the dead symptoms.
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Later I re-assembled the power board and applied the power and this is what I saw.
Have a workout week my friends.
Humphrey Kimathi is from Nairobi Kenya and the author of:
5) Basic Electronics course.
He is also a blogger at Electronicsrepairmadeasy.com
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