Question HP EliteBook 840 Powers on immediately no boot, CAPS constant on

[tommyhardon]

I have a HP EliteBook 840 that powers on immediately upon connecting a charger. The system does not boot, the CAPS keys is constantly on. The power LED is on. The fan is not spinning. The CPU is heating up. The power key does not power down the device.

Has anyone seen this before?

 

[BEAUFORD_SAVAGE]

I have been fixing electronics, including computers my entire adult life. I have an engineering degree to be able to understand how things work, and why things fail.
That said, your very SPECIFIC combination of symptoms, no. And there is an infinite set I have not seen as well, that does not mean I can't fix them. It's just a matter of if they are worth fixing.

THAT SAID.
It almost sounds like a power switch that is always in the on position. But in computers, that would force it to shutdown again, and restart ad infinitum.
This is NOT a software problem, this is absolutely a hardware problem. Now the question is what hardware?
Has it seen a spill anytime in the past? It sometimes takes a while for the corrosion to create a "circuit" that causes this kind of failure.

You have nothing to lose here, if you don't think it is worth the $ 300-400 APPROXIMATELY a shop will chrge you to change the motherboard.
SO..... watch THIS VIDEO which will show you how to take apart your computer for further inspection. Often problems are visible, and can lead you to a fix, sometimes simple. No guarantees. Take it apart just far enough to be able to examine the top of the motherboard with the keyboard off. You may need to remove a few other items as well . I would be looking at where the power comes into the mommy board, and really, just a very CLOSE inspection of the MB. (motherboard
) It could be a visible foreign piece of something conductive like a staple, or a invisible dead IC or corrosion. The Idea is to root out any visible issues, for instance a common problem like bad electrolytic capacitors.

 

[tommyhardon]

It is a system board issue. I was able to acquire a replacement system board and that one worked. So this also rules out the power switch from being stuck in any fashion. Usually in a short circuit of a system board will just power off or not start. The CPU is heating up, but there are no POST codes presented apart from the constant on power LED.

PS. Despite replacing the board for testing purposes I'd still like to get to the root of the issue with the original board. So I'm open further suggestions etc.

 

[BEAUFORD_SAVAGE]

FYI, if you read what I said "It almost sounds like a power switch that is always in the on position. But in computers, that would force it to shutdown again, and restart ad infinitum. "
That means I said it could NOT be the switch, Then I said, in so many words ..... it HAD to be the motherboard.

"PS. Despite replacing the board for testing purposes I'd still like to get to the root of the issue with the original board. So I'm open further suggestions etc."

That depends on a few variables, Do you have expertise in electronics?, Do you have a multimeter? Without being able to power it up, you are mostly limited to a visual inspection for bad capacitors, metering out semiconductor power supply components that are not integrated, etc. The reason that the a component failed could be too many to mention really.
And would be a waste of my time, as I could help people who could actually get their machines running.
I actually specialized in Failure Analysis to component level for years. But that had the purpose of helping the engineering dept. make better products.

So if you want to do an autopsy yourself, go nuts, I am going to help others that need it.