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Reversed Polarity on DC Power Supply. Can I replace Fuse/Diode on MB?

Hi,

I managed to reverse the polarity on the DC input for my laptop (cheap travel power supply with adapters). Laptop went out, reboot via battery was possible and the laptop ran until the battery was dead.

My hope is that i just smoked a fuse or a diode protecting the mainboard itself. I took the laptop apart to take pictures of the DC input area.

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I have some experience in soldering (little in SMD), have a multimeter and an oscilloscope to debug.

Ordering a new board doesn't make sense compared to the price of a new laptop.

Motherboard Model is 60NB04Y0-MBB030.

Answer this question I have this problem too

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3 Answers

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I know its a little bit to late, but if you still have the board and want a spare ;0)

I will think the problem can be one or both mosfets (the square ones with 8 small pins) at your first picture) There are 2 mosfets together and I will think one or both of them doesn’t work proberly.

I have a ux303ln here and the first mosfet qm3024m in the dc-in way after the power jack was shorted.

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Check if the power supply is dead. You can always pick another travel adaptor. As far as I know, laptops as the voltage is given by the power supply, don't use any fuse. It's quite difficult to diagnose smd problems specially on laptops, because the components are pretty close one to the other, but you can check if any part is burnt by having a look to it.

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I know it’s late, but I have the same problem, and feel obligated to document the process for anyone else. I reversed the polarity, and have precisely the same symptoms as you described. I decided to run the power backwards again (can’t kill it twice, I hope) and felt around with my fingers for any components that were heating up (MOSFETs tend to fail short circuit). I noted the chips shown heated up (see attached) and so I will try to replace them, and see if the problem is resolved. I’ll report back with the results. (Ignore the wires and glue, the DC socket broke, and this is a temporary bodge to feed power to the laptop.

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Comments:

You don’t think the problem is at the other side at the pcb? Often is it the first 8 pins mosfet there are destroyed internal. It can often be fixed with a bypass wire(drain to source) because there is a working mosfet after the first one. So you don’t have to replace the destoyed mosfet ;0)

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looks like your "chips" are diodes (hard to see on this picture). would makes sense that they get hot with the reversed polarity.

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Jo Womp will be eternally grateful.
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