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HP n5420L with internal short circuit

Last response: in Laptop Tech Support
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January 17, 2011 2:14:40 AM

Hello,

My sister asked me to check out a HP n5420L notebook. When I got it home nad plugged in the power adapter the power LED on the adapter went from steady on to a flicker every 2 seconds or so. The adapter seems to have normal voltage output at no load and powers a 12 volt automotive bulb without a problem. The adapter exhibits the same behavior when it is shorted out as when connected to the laptop suggesting there is some sort of short circuit in the laptop. Anyone have any experience with this issue?

Thanks!
a b α HP
a c 572 D Laptop
January 17, 2011 12:40:40 PM

Hello xrayangiodoc;

This HP n5420L is approaching 10yrs old, is it not? It would need to have a lot of sentimental value to go through all that troubleshooting.

Try removing all the components that don't need to be attached to get powered up. HDD, CD drive, floppy drive, PCMCIA cards, USB devices, miniPCI cards are examples. Also remove the battery. Any of those might be the cause of a short circuit or other reason to prevent power up.

Then you can start out doing a visual inspection of the motherboard components. You'd be looking for obvious signs of damage such as bad caps (capacitors), burnt resistor, maybe a sign of dried liquid residue or broken solder trace. A good light and a low power magnifying glass would be handy.

After that you're probably going to need to use a multimeter to look for a short circuit.

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January 18, 2011 1:50:01 AM

WR2 said:
Hello xrayangiodoc;

This HP n5420L is approaching 10yrs old, is it not? It would need to have a lot of sentimental value to go through all that troubleshooting.

Try removing all the components that don't need to be attached to get powered up. HDD, CD drive, floppy drive, PCMCIA cards, USB devices, miniPCI cards are examples. Also remove the battery. Any of those might be the cause of a short circuit or other reason to prevent power up.

Then you can start out doing a visual inspection of the motherboard components. You'd be looking for obvious signs of damage such as bad caps (capacitors), burnt resistor, maybe a sign of dried liquid residue or broken solder trace. A good light and a low power magnifying glass would be handy.

After that you're probably going to need to use a multimeter to look for a short circuit.



Thanks for the reply. I took out the battery with no effect on the problem. I'll look into the rest of the options outlined in your post. I'm retired so I have lots of time to play. Keeps the mind engaged.
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January 25, 2011 2:00:43 AM

I tore down the laptop to the motherboard. The short seems to be localized to the power jack but I can't seem to get the mainboard out of the case to access the connections with the power jack. Too bad. Funny how the power jack of my Averatec laptop was so much easier to access than the HP.
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a b α HP
a c 572 D Laptop
January 25, 2011 10:34:49 AM

Have you dropped into the HP support forums and asked around there?
You might get lucky and find someone with the right experience or knowledge to take the next step.
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January 25, 2011 7:07:58 PM

The most I found at the HP site were instructions on how to replace the hard drive. I'll look again.
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