z420 does not start, full speed fans without screen

[MrNico]

Hello, a while ago I had the same problem, and I solved it by changing the CMOS battery, again, with the same problem, the solution was to reflash the BIOS, but now, I have no idea what could be happening. When I turn on the device, it doesn't make any sound, if I turn it on without a video card, it doesn't make any sound, if I turn it on without ram, it does make some beeps. Currently I cannot start the computer in any way. When I move the jumper to start "Crisis Recovery" the PC gives 5 beeps, but if I leave it as it was it just turns on, waits a few seconds and the fans start working at maximum. What ideas do you have? that can help me.

I need to mention that sometimes, very rarely, the device turns on without problems, but when I restart it, it generally doesn't turn on and I spend days doing things until it turns on.

[SDH]

I'd say your motherboard has been slowly failing, and finally has failed.

It is quite easy and inexpensive to transplant in a recycled Z420 motherboard from eBay... takes me about an hour, not rushing it.

Two things to know:

One, if the motherboard is brand new then it will not be "branded" for Windows use, which makes the whole process more complex. Statistically your new-to-you motherboard will already be Windows-branded, rather than Linux. Can be either way, and you really don't know ahead of time. If you're lucky it will be Windows-branded and already listed in the combined Microsoft Windows 10/11 registration server and have a digital license there that will work for W10 or W11 already. On first contact with the web it will auto-activate in that case.

Two, there are v1 and v2 Z420 motherboards. Regardless of what you started with you'd only want a v2 to transplant in. I've posted in here on the motherboard's bar code label and what the numbers are on the right-hand side of that label to ensure you get a v2. Those can run both the v1 and v2 (faster/better) processors and fastest memory to match.

If you happen to get a Linux branded motherboard you can buy an official Microsoft "OEM"system builder W10Pro64 optical disk and "key", unopened, off eBay for about 35.00 USD and enter that code after installing the OS. Be careful as you scratch off the thin covering MS puts on over the first set of numbers... they make it fragile and easy to ruin. I install disconnected from the internet to get a local account only... when you reconnect the first time the code you entered will activate on that motherboard and auto-generate you a "digital license" for it that will work based on that motherboard's UUID in the future. That will also allow you to also upgrade to W11Pro if you wish. Both DGroves and Paul Tikkanen recommend the Rufus method, and I like that too. Below is a good recent video because the Rufus method keeps improving and changes a bit over time.

On the last Rufus page that shows up as you begin triggering the install I check all the boxes there, and I do the install disconnected from the internet.

Before you start any of this make sure that the HP BIOS is first to factory defaults. And, I personally make sure my BIOS is at the latest version... way old BIOS could not even run some of the newer processors or the Z Turbo Drive cards. Also, doing a clean install is important for both W10 and W11. I discovered that doing an upgrade (instead of a clean install) drags some old drivers along from the original install... not ideal.

https://youtu.be/7ff8jsOyoIk