HP Z420 randomly shuts off

[M491]

Hi all,

I have a problem with a HP Z420: it randomly just switches off. No error messages, it's like someone simply pulled the plug. It sometimes works for a few hours and it sometimes stops right after switching it on, there's no discernible pattern. This system ran rock solid for the last three years since I bought it.

There are a few similar posts on this board, and from their suggestions, I already tried:

• re-seating RAM, GPU and so on
• removing all peripherals
• resetting CMOS by jumper
• running a memory check (came back without errors)
• checked fan and temp sensors (showed all perfectly normal values)
• checked if there's a short somewhere (to the best of my abilities)

So far, no joy.

Has anybody any other suggestions what I could try? I realize it's getting a bit long in the tooth, but still... the fact that it sometimes stops right after switching it on - before I see a BIOS splash screen or anything else - makes me wonder if there might be just something wrong with the power supply, would that fit what I'm describing?

Thanks,

Marc

[SDH · Accepted solution]

Sounds like a power supply issue to me also. Have seen this before, very rare, fixed with eBay replacement power supply. Never have had a HP replacement power supply go bad over the years and it is uncommon to see their power supplies go bad but it does happen.

There are 2 Z420 power supply ratings... 400W and 600W. Only get the 600W one. If you look on the power supply label in the eBay ads, you also can see that there are revision numbers too. I've chosen to get the later revisions. The one below is Rev 6. You can see the upper HP Assembly P/N and the lower Spares P/N. Same item, just how HP does it, search under both for the best deal. Expect to spend about $50.00 USD. Replacing the original is quite easy, and I do think this is fixable.

[M491]

Thanks for the detailed reply, much appreciated!

I'll check around if I can find one that I can return, should it turn out to not be the cause of the problem after all.

I'll post the result when I know more.

[M491]

Ok, I got my new not-so-new power supply, replaced the old one and the Z420 is running without a glitch again. Let's hope this one will last a bit.

Thanks again @SDH for confirming.

[M491]

And just after I post this, it happens again ☹️ The workstation switched itself off, then on again three or four times, and then booted back to the login prompt.

So I have to take it back, it was NOT the power supply.

If anybody has any other ideas...

[SDH]

Personally, I'd now do a Z420 version 2 motherboard transplant. We have posted here on how to find a v2 from the barcode label often shown in the eBay ads. I can refresh the info on that if you can't find the prior posts... the key is the part number on the right-hand side of the bar code label. 

Or, if you have a bit more spare cash, give up and buy a Z440 off eBay. Those are a quantum leap or three above the Z420 v2, and there is no v1 vs v2 issue with those. 

[M491]

Yes, I'll probably buy a Z440, they have pretty reasonable prices on ebay. And I finally get my notebook back, which had to fill in for the Z the last few days 🙂