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compaq laptop nc8000 wont start

by cloturoloco / March 27, 2007 1:41 AM PDT

Hi, everyone.

i have a laptop compaq nc8000 it was working fine but then it went to stand by and it wont start again, i can heard the fan and hard drive working, then I when i tried to restart it , the laptop flashes green lights for several seconds and then powers down, even with the power cable connected to it, the fan would run for about 5 secs and then system would shutdown.
I do not get any error messages so i can tell what is the problem?.
i was able to re-start it once after many tries every 15 minutes, i checked in the event viewer and everything looks normal there. I was able to use it but if it goes to stand by it does the same as I said above.
I have not installed any new components or software.
I have win xp pro.

I'm thinking also that the voltage regulator is faulty because it happened before once and the symptoms were similar.
Can somebody tell me how to disamble the laptop to get to the voltage regulator?, I have a service manual but it does not say anything about it, I just want to know if I have to remove the top or bottom cover to get there.
Thank you for your help and time.

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See flowchart 2.2 at link.
by R. Proffitt Forum moderator / March 27, 2007 1:50 AM PDT
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See flowchart 2.2 at link.
by cloturoloco / March 27, 2007 2:10 AM PDT

No, I dont think mine has a reset button or Standby switch but i will take another look, I already tried to reset it using the power switch.
i will take a look at the file that you send me to.

Thanks for your help and time

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Then it's not a laptop?
by R. Proffitt Forum moderator / March 27, 2007 2:14 AM PDT

Sorry, you've stumped me. The lid switch is the standby switch and the reset switch may or may not exist but on the laptop model nc8000 it should have a lid switch.



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by cloturoloco / March 27, 2007 2:31 AM PDT

Ok, what you mean by the lid switch is the little button that get press down when close the laptop, yes i tried that too but nothing happens.
Right now the laptop wont boot, i have been trying for the ast 3 hours, I am really thinking it has again a problem with the voltage regulator.

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If so, do you have the background?
by R. Proffitt Forum moderator / March 27, 2007 2:38 AM PDT
In reply to: ok

I've seen few in this forum with the needed electronics background and tools to do the repairs. Not that you don't but it is rare. It's that nagging thought that if you had the background you wouldn't ask these questions.

No offense intended but if the regulator was the issue 99% of our members would know to take it to some repair shop like or if a new power supply brick (that external unit) didn't help.


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I think i can do it
by cloturoloco / March 27, 2007 3:01 AM PDT

Yes i have tools and i have a diploma in electronics but not in computers, so i can test the system to see if there is something wrong, I just want to minimize my work by not disambling parts that I dont need to.
I just want to know now the steps to get to the power supply.
i do not have the money to take it to a repair shop and anyway they always overcharge their job in my experience.
Thanks for the help

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There are multiple power supplies
by R. Proffitt Forum moderator / March 27, 2007 3:19 AM PDT
In reply to: I think i can do it

1. The first and easiest ts that external brick. Use your voltmeter and check that it's in spec.

2. Inside the laptop is going to be hairy and I will not help there because of the liability issues. However I use my oscilloscope to check the output to the battery and see if it's acceptable. What's acceptable? I'll write within a volt of the battery voltage. That usually is good enough to write the battery charging circuit off.

3. Most if not all laptop makers do not provide schematics so you are left to think over how most generic switch mode power supplies work. Then we trace the circuit and look at what nodes we recognize for voltages and waveforms that we then guess if they are proper or not. The reason for guesswork is that not many makers hand out schematics today. But they do use pretty much the same circuits over and over so after a few hundred repairs you can build up your knowledge base of what a signal or voltage is when you probe with the scope.

Good luck,


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by cloturoloco / April 3, 2007 9:54 PM PDT

The external brick is fine. I checked already.
yes the schematics will be great but they are hard to get, I guess I just try and see what do I think is not normal.
Thanks for your help and time.

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"they are hard to get"
by R. Proffitt Forum moderator / April 4, 2007 1:31 AM PDT
In reply to: thanks

No, they are impossible to get. This is why a background in electronics design helps. You take your common switch mode power supply design and apply that to your trouble shooting skills to essentially reverse engineer what they implemented.


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