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Disclaimer: I'm sort of a noob, and this is a long post. Thank you all in advance!

summary: completely dead laptop with no signs of life whatsoever (suddenly, for no apparent reason)

Here's the deal:

Lenovo Y470 (a few months past warranty with no water or shock damage). It stopped working suddenly (no lights, no sound, even when connecting adapter with or without battery).

I tried a different adapter (same electrical rating), but no luck.

I disassembled the thing completely, and tried plugging in the adapter and looking for signs of life with all different combinations of components installed (tried all combinations of RAM, CPU, USB power cords, screen, etc plugged in).

no luck. Then, I noticed (as I was plugging in the adapter to try for the millionth time) that there was a "spark" for an instant when I first connect the adapter to the power jack. The adapter's LED would then flash (indicating it isn't working or charging). So, I thought the power jack has a short of some sort (due to bad soldering or something). Scanned virtually every single component on the motherboard, and tested the power jack connections with a multimeter. No shorts or damage to anything on the entire motherboard.

Now I'm thinking I need to replace the motherboard.

But, my actual question: What does this "shorting" when connecting the adapter signify? (btw, the voltage across the power connections and current through it drop to virtually zero when the adapter is connected and "sparks", and they stay that way). The bewildering thing is that there are no damaged components, and the voltage across adapter terminals returns to normal after I disconnect it (so it's not damaged).

Please take a look at the pictures (of the motherboard's power connection and nearby components) and see if I'm missing something completely obvious...

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Motherboard model: LA-6881P

Laptop model: Lenovo IdeaPad Y470

Hennes
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Cashew
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2 Answers2

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Is there any battery installed in the system (CMOS or regular laptop)? I had an Epson laptop with an external battery that would behave that way (the LED would): If you plugged it in it would light up, but as soon as you tried to turn it on, the light would die. I suspect in your case, the battery is discharging slightly through the cable when it is connected.

K.A.Monica
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The spark when connecting the adapter is more-or-less normal for a capacitive load. However, the fact that the voltage goes to zero would indicate a damaged adapter, a short in the internal power cable, or a shorted mainboard.

You reportedly tried with a different adapter, so it's probably not the adapter. (Did you check the on-board voltage with the alternate adapter?) You can connect the internal power cable to the adapter but leave it disconnected from the board, then meter, to see if the internal power cable seems OK.

But if the adapter and cable check out it's sounding a lot like a bad mainboard. The disk drive or DVD drive could possibly cause the short, but if you've tested with those disconnected (and also presumably looked for obvious external shorts between metal components and the mainboard bottom) then the mainboard is strongly suspected.

I think you gave it the old college try with this, but one isn't going your way.

Daniel R Hicks
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