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LED inverter capacitor burnout

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01ago

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Hi all,

I was trying to replace my 14.1'' old laptop CCFL backlight with a LED strip I bought on eBay. While replacing the inverter, I measured the Vin on the motherboard to be 20V. Although it's stated on the inverter that the input voltage can be 5-20V, the moment I connected the power cable to my laptop, a little yellowish block on the inverter burnt out (see pic), with some smoke and smell. I'm a newbie in electronics - some search on the Internet tells me it is a tant capacitor and it burnt out because the 20V input exceeded its voltage or current rating. Now the seller sent me a new inverter board and I need some help on what to do with it. I guess I should put a resistor in series to limit the current? But how many ohms?
I'm not sure about the ratings of the capacitor either - the code on it reads 106V, 105K4. Can someone tell me what this indicates and how can I make it work with 20V input voltage?
 

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LED's use very little voltage compare to cfl's, I don't think you can just repace it with led strip, you will have to modify the circuit meaning regulate the voltage and current the leds need and I am not sure of brightness, if it will be the same or more or less, but it will be interesting if it works.

01ago said:
Hi all,

I was trying to replace my 14.1'' old laptop CCFL backlight with a LED strip I bought on eBay. While replacing the inverter, I measured the Vin on the motherboard to be 20V. Although it's stated on the inverter that the input voltage can be 5-20V, the moment I connected the power cable to my laptop, a little yellowish block on the inverter burnt out (see pic), with some smoke and smell. I'm a newbie in electronics - some search on the Internet tells me it is a tant capacitor and it burnt out because the 20V input exceeded its voltage or current rating. Now the seller sent me a new inverter board and I need some help on what to do with it. I guess I should put a resistor in series to limit the current? But how many ohms?
I'm not sure about the ratings of the capacitor either - the code on it reads 106V, 105K4. Can someone tell me what this indicates and how can I make it work with 20V input voltage?
Click to expand...
 

I probably did not make myself clear enough - there is an inverter that comes with the LED strip to replace the original inverter for the CCFL, to provide the suitable voltage and current for the LEDs. And the problem I'm having now is the input voltage from the motherboard caused the new inverter to burn out.
 

Tantalums are notorious in terms of not liking overvoltage. Even small voltage spikes above their rating will cause it to die violently. From what I can see, this is a 35V cap, probably needs to be derated to about 25V or below.

Putting a resistor in series is probably not a very good solution and may cause your inverter to run unstable. Either just plug your new unit in and hope for the best (if Vin is indeed 20V and no ripple or spikes are on it, I suppose it should work) or replace the tantalum cap with a higher rated one.
 
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    01ago

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Hi pradeep and Ice-Tea,

Thank you for your advice. I've tried the new one on, and it worked! The LEDs lit up. So it must be some defect in the previous one.


Best wishes.
 

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