Z420 Shutting Itself Down and solid green HDD light on front

[seanyp]

Hi,

My Z420 recently shut itself down and was displaying a solid green HDD light on the front. It was initially unresponsive when pressing the power button but the green light went away after I held the power button on for ten seconds or so. It would then start the boot sequence but cut itself out before getting to the Windows screen. 

I removed and cleaned all the fans (they were pretty clean anyway), removed and reseated the RAM and GPU then removed, reset and replaced the CMOS battery. When I put it back together it booted up and was running fine for a day or so before shutting down again. I had HWMonitor running during that day and everything seemed to be running fine. 

This morning I removed and reseated the CPU with new thermal paste (and also tried a new power cord) and it booted up  ok. I ran a HP Diagnostics test and CPU stress test and it passed everything with a MAX cpu temp of ~75degrees so I hoped that was it but  it has now just shut itself down again. 

I'd be grateful if anyone could help suggest any other ideas or troubleshooting steps or if anyone has had a similar issue.

Thanks in advance,

Sean

[Brian1965 · Accepted solution]

Hi Sean,

Can you please specify what CPU model is installed in your Z420? Below are a couple of compatible Z420 CPU models and their respective maximum CPU heat spreader temperatures. If your CPU exceeds the listed Tcase value your system will shutdown.

[seanyp]

Hi Brian,

Thanks for getting back to me and sorry for my late response, I missed the notification that someone had replied.

Yes that must have been what was happening. The CPU is the 1650v2 and I didn't realise they had such a low CPU heat threshold but it has now stopped happening since the new thermal paste has bedded in. To be honest the machine is rarely under any excessive load and the case and fans are always kept off the ground and pretty clean but the thermal paste must have just deteriorated over time. 

Thanks again for getting back to me and providing those thermal thresholds, that's good to know. Nice rig setup yourself btw 👍

Cheers,

Sean

[SDH]

Sean,

Brian is a master of souping up these workstations. I believe he is still running W7Pro64 in order to use the Intel overclocking software. That utility seems to no longer work under W10 and W11. I also did not know of those low heat thresholds for some of the v2 processors... good info.

Here's a processor cooling tip for the Z420 and single-processor Z620 builds: It turns out that the Z440 uses a processor heatsink/fan combo that has almost exactly double the cooling capacity of the original heatsink/fan combo in the Zx20 workstations. It fits perfectly including if you use the Z420 optional passive front airflow cooling guide (663070-001) and it also fits perfectly under the single-processor build Z620's "saddle" (644316-001) that carries the front/rear memory bank's cooling fans. The trick to just using it as is (for about $15.00 from eBay) is that they come stock with a 6-pin motherboard header fan plug. You just use the first 5 holes in the plug. As you know a standard PWM fan uses 4 pins with pin 1 being ground. HP added a 5th hole for a ground jumper wire from pin 1 to 5 in the Zx20 family and added a 6th hole for a ground jumper wire from pin 5 to 6 in the Zx40 family. There is room to just hang that 6th plug hole off the end of the Zx20's 5-pin motherboard header. Here's a pic of what these look like, and the eBay part number to search for is 749554-001. These have worked great for us in our souped up single processor Zx20 builds:

Double cooling capacity Z440 heatsink/fan

[seanyp]

Hi SDH, 

Thanks very much, I've just ordered one of those! Thanks also for taking the time to provide that info about the pins, looking forward to getting it installed when it arrives. 

When it started playing up I was half-tempted to use it as an excuse for an upgrade but when I stripped it down it was still pretty much as new. They're really well thought out machines and runs pretty silent for my needs so I'm going to add this heat sync, keep an eye out for a new GPU at some stage and put the money saved towards a nice family holiday I reckon! 

Thanks again to you both for the support, much appreciated.

Cheers,

Sean

[SDH]

Sean, 

The Z440 is a nice upgrade to consider. They've really come down in cost as have their processors and memory. Plus they can run with the NVMe M.2 drives using the HP Z Turbo Drive G2 PCIe card. You're Z420 still has lots of life left.

Happy to help. Since you'll be back "under the hood" again installing that Z440 heatsink/fan let me share what thermal paste I use. I know Brian has another favorite but can't find his reference to it. We here have been using the original Noctua NT-H1 for years and I've never seen it fail. They later came out with their NT-H2 and I tried that but it did not spread near as well so switched back. Everyone has an opinion on what to use and how to apply it, but the NT-H1 stuff is the best for us. I only buy the small 3.5g tubes... that way they're freshest and will provide enough for a good number of processors.

When you're cleaning the top stainless cover of old paste make sure to have some cloth or paper towel beneath to protect the bottom electrical components.

Keep us posted on your progress if you can...

[seanyp]

Yeah I was actually looking at a few of those and surprised at how much they have come down in price funnily enough. Just hard to justify at the moment when I don't really "need" it as such but I'll find an excuse sooner or later! 

Thanks also for the recommendation, I'll get a tube of that also. To be honest I've had the machine for ~5 years and as far as I'm aware it still had the original paste on the CPU so it was (obviously now in hindsight) well overdue a freshen up. I used MX-4 which is what I've always used before but I'll give that NT-H1 a try. I've just had a quick nosey and the other reviews look great also.

Many thanks again for your time and advice.

Cheers,

Sean