Laptop won't turn on (replaced charger and battery)

[Harmont]

I have an HP ProBook 450 G5. It was completely fine, until I left it sitting on a shelf without charge for a few months. When I tried to turn it on, it would no longer boot. I attempted the following troubleshooting steps:

1. I tried to hold the power button to reset the battery, which caused power LED to blink, but didn't fix the issue. At some point I could no longer get a reaction from LED either, assuming the battery completely discharged.
2. Laptop also wouldn't charge (no light on power LED), so I thought maybe the charger was dead. I replaced it, but laptop still wouldn't charge.
3. So the next logical step was to replace the battery. Which again made no difference.
4. I even replaced the charging port, which also didn't help.

So I'm lost at this point. Not sure if ProBooks can work with battery disconnected, but I tried to plug AC power without battery and laptop still wouldn't turn on.

Thought on what else I can try? Maybe it's a dead motherboard, but not sure how that would happen if laptop was simply sitting on a shelf for a few months.

Any help much appreciated.

[erico]

Remove the battery and then hold the power button for at least thirty seconds. 

Connect the new battery and plug  in the power adapter.

Let the battery charge for a few hours.

After a few hours, press the power button to see if the notebook reacts.

Since, as far as I can tell, your notebook uses the main battery to provide power to the BIOS, it probably will not power on in the case of a battery that no longer held current.  It may power on after you have let the battery charge for a few hours.

[Harmont]

Haha, I suppose I'm blind. I just did as you said. It didn't help in any way, but I noticed that the laptop was hot in a particular spot next to the exhaust fan. So I opened it up again and saw a very noticeable burn (photos below of the motherboard, as well as the keyboard which sits directly above it). So I suppose it's a motherboard replacement?

Can someone enlighten me what has actually burned there? I assume LVDS is where the monitor connects to. Maybe there's some integrated video chip there?

And how the hell could that have happened?

[Harmont]

Okay, so I've pulled it apart. That's what's on the other side. Not sure what this was (maybe a capacitor?), but looks like it blew up, even making a hole in insulation tape. Should I consider HP laptops an occupational hazard from now on? 🙂

[Harmont]

New motherboard for i5-8250 version costs AUD$500:

https://www.ebay.com.au/itm/324528607984?hash=item4b8f6992f0:g:M2cAAOSwnIpgVFXQ

Considering brand new 450 G5 can be bought for AUD$600, sounds like it's a wrap: https://www.dicksmith.com.au/da/buy/australian-computer-traders-hp-probook-450-g5-intel-i7-8550u-180...

[erico]

Wow! 

That is depressing !   Yeah. Does look like a wrap on that one.

Unfortunately I could not  possibly see what happened as you were replacing the battery.

It is possible and also unfortunate that an inadvertent shorting of a component could have happened.

[Harmont]

Sorry, I think I confused you there a bit.

I went back to the photos I took when I first opened the laptop and those burn spots where already there (I just didn't notice them), before I even attempted to replace anything. So I think that was the original reason why the laptop died.

Burned component is covered by the black insulation layer (can be seen on the attached photos). I assume it would not be possible to short it, as you can't even access it without removing insulation. Also, it's on the back side of the motherboard, which I removed yesterday first time. Considering all of the above, it's highly unlikely was self-inflicted.

Could be overheating, but then we would see reports from other people using the same laptop. And I found none. I've also checked the fan and it's decently clean.

Last thing I can think of - manufacturing defect.

Any thoughts what would be the most likely reason for that to happen? I've seen bulging capacitors, but burning/blowing components is something I've never seen on motherboards before.

[erico]

You didn't confuse me.

I t would have been a good idea to have made a larger image that shows the entire side  of the system board. That would have let me know in which section the damage was in.

Well, the system board is smoke checked anyway, and  given  your description of the issue, it is likely that voltage regulation chips and capacitors have blown.  I do see destroyed caps, resistors and diodes in one of your images. I can see them in an image moderation console which is not available to you.

" I've seen bulging capacitors, but burning/blowing components is something I've never seen on motherboards before."

Components do fail.   Those of us who have worked on electronic devices have seen them before. Do you have power surges in the household current where you live? Power surges can cause this to happen.

[Harmont]

I run expensive electronics through APC Line-R voltage regulators at my house. So I would put power surge in the "highly unlikely" category as well.

I bought this laptop in May 2018 and it served me about 3.5 years. I realise quality of components keeps going down over time, but to be honest I expected a bit more from ProBooks.

Either way, I checked prices again and realised that AUD$600 was for a model with integrated graphics. Mine had discrete, so it's about AUD$750 instead. But then I also noticed it's a refurbished model. If I were to buy a new one (which is G8 today) it would cost me about AUD$2000.

It made me think that maybe replacing the motherboard is not such a bad investment, so I bought a used one for AUD$400. Fingers crossed it will get the laptop back to life. I'll report it back once it arrives, if I don't forget.

[Harmont]

Here is a better picture of the burned part of the motherboard, basically next to the Nvidia chip:

Googled a picture of the same motherboard and looks like it was a small resistor sitting next to a voltage regulator: