Help! Laptop Power Problem!

pryde7

Kindly help me out. I just ripped open my old HP laptop that has a power problem (cannot power on). I've measured the voltage from the dc input on the board which measures approx 2.3V instead of 18.5V. The AC adapter works fine on another laptop.
I'm stuck and don't know which of the tiny components is drawing all the voltage. Normally it should measure 18v inside. I do have a fair knowledge of electronics but this one is above my head.
Please I really need some help!!

hetty

What voltages are you getting out of the power block and the battery when its unplugged?

pryde7

The voltage is 18.5V as rated on the adapter,
The problem is probably from inside, when plugged and u measure the dc contacts from inside it measures 2.31v.

hetty

When you say the inside, I have no idea where you are testing the DC voltages from but I would check the battery voltages when it is unplugged, as its as good as any place to start with power problems after the power block. It can sometimes be hard to test the connectors on a laptop battery, use electrical tape and paper clips on the multimeter probes, it works a treat.

pryde7

Inside...I mean I'm working on the motherboard.
When the adapter is plugged in the input voltage measured from the DC plug connectors on the board is very less...kind of draining!!
Probably a component is causing this, but I cannot really locate it.

hetty

Yeah I knew it was motherboard just not where you are checking this. But, seriously check the battery first before you go blaming any components on it, power goes through the battery and if its defective then it might be causing the shortage of voltage. If you check the battery you should be getting about 15 volts out of it. If it is motherboard components then the scrap heap is probably the best place for it and buy another one.

pryde7

If it is motherboard components then the scrap heap is probably the best place for it and buy another one.

You make me laugh...but seriously its not yet time to scrap it! The fact is, the battery is out of this cos the laptop should come on without the battery.
If i can know the damn component that is causing it, even if its an IC I can get it fixed.

hetty

If youve got the skill to fix faulty motherboard components then all 'power' to you

How old is it? And what model is it?

pryde7

HP Dv4000! I want to explore all options before announcing its death.

hetty

Check the solution by palamino2003 as a possible work around


Another source of suggestions

No power.

Cause: Bad voltage regulator, bad capacity, bad diode, bad power chip, bad bios, bad BGA (Ball Grill Array) controller chip, Vcc shorted to ground, liquid spilled, cold solder.

pryde7

Tnx man, I'll give it a try!

hetty

Try to check it with the battery plugged in if you can. Ive used some laptops that had to have the battery plugged in before it worked off the mains power. It should work without but they didnt, dont know why.