Noisy z420 again

[rcddk]

So I bought this z420 (E5-2660, 64 GB RAM, 5x 4TB disks) for a FreeNAS in my home, but it is way noisy. I know about the bios adjustment, but it's already at the lowest.

I've disconnected fan by fan, and the CPU and memory fans are really quiet, no problem there.  The problems are the back chassis fan and the psu fan.   If I unmount the chassis fan it is actually quiet also, so I think it is that plastic contraption HP has put it inside, that works as a resonance chamber so I 'm thinking I will buy a slightly larger, maybe Noctua, fan that fit to be screwed directly onto the back chassic, and then drop the plastic stuff.  My memory sticks all have built-in cooler plates anyway (not original HP memory). 

Then there's the psu. Same idea, get a Noctua and replace the internal fan. Problem is, I can't seem to open it.  I have opened endless psu's before, but even though I have removed all screws, it still is one solid block. Anyone who can give me a hint how to get it apart?  Not just out of the box, but open the psu itself.

[SDH]

First off.... the rear 92x92x25 mm case fan has 4 standard spacing holes in the case for regular case fan screws, but HP never put screws in.  We put the 4 screws in place, and it stops the resonance and buzzing that happens if things are not as secure as they could be.  Note below where the missing screws should go:

There are two power supplies... a 400W and a 600W version, and we have found the 600W version to actually be a bit more quiet.  Probably significantly better build quality, and we upgrade any 400W power supply to the 600W version in this workstation.  eBay is your friend at about $45.00 including shipping here in the US.  It is easy to tell them apart:

[rcddk]

Hey thanks for the quick update!

Good tip on screwing in the fan, I will try that!

About the PSU - I already have the 600W version, but I think it is still noisy.  Any idea how to take it apart?

[Z440Roger]

The Z420 is normally a very quiet machine and when the chassis fan and the PSU fan speed up there is a problem with the temp sensor that is placed were the power button is. I have sold HP Workstations and everytime a Z4X0 or a Z8X0 have chassis fan/s speeding up the issue was the temp sensor.

I would try to replace the sensor before adding third party fans. If you add third party fan as a chassi fan the motherboard will detetct it and warn you at every startup.

[rcddk]

It actually speeds up when powered on, to the point where it sounds like a vacuum cleaner. After that it settles down to a RELATIVELY very much more quiet level  - but still way to much for my taste. I think the problem is everybody have a different idea of what is quiet.  

I have now screwed the back chassis fan as suggested by SDH, and that has taken care of the grinding edge noise from that fan. I still hear it, but I can live with it.

Only remaining fan noise now is from the PSU. 

How bad it is. Well I sit next to the server, and I can have a normal conversation without having to raise my voice -but when I switch it off my ears are ringing (tinnitis) so it definitely is still too loud.  Like I said, I think the problem is just that everybody has a different idea of what is too noisy.

[Z440Roger]

It actually speeds up when powered on, to the point where it sounds like a vacuum cleaner.

That´s not normal and has nothing to with "...everybody has a different idea of what is too noisy.".  These are very quiet computers that are almost dead quiet, literally, when powered on. I have sold HP Workstations and when a Z400/Z420/Z440 and it predecessors behave like yours it has always been due to a faulty temp sensor. Replacing it solved the issue directly. (HP Part number 663218-001)

[SamirD]

Unless you need physical access to the system case, I would suggest to simply move it far away and use kvm extension cables--problem solved. 🙂

[rcddk]

Z440Roger, I think I owe you an apology...

I lived with the noise for some weeks, but it really give me tinnitus - my ears are ringing after spending just a few minutes next to the server.  Finally I took the server apart, removed everything that could whir, until the only thing remaining was the PSU - and that was indeed the noisy bit.  I then did some more close-up experimentation, turning on the server while monitoring the PSU closely, and for the first few second I can see the fan spinning. Then it accelerates to 100% for a few seconds, then fall back to maybe 20-30%. I'm of course guessing here, but just to give you an idea of the noise level.  

So the next step is trying to locate that temp sensor.  When I dislodge the power button on the front of the cabinet, there's a switch, a blue power led and a green disk activity led. I don't see any temp sensors anywhere though. What does it look like? Do you have a picture perhaps? Never mind, I found it attached to the front cabinet at the bottom, next to the speaker. It looks like a transistor.   I'm wondering, could I just snip it or short it to check if that makes a difference? 

I just checked Ebay for the HP Part number 663218-001, with shipping that's almost $50 here, I can buy a new cabinet for that price. Sorry I'm a hobbyist. Do you know the details of the sensor itself?  Maybe I could just replace that instead of the whole switch assembly.  Never mind again, it's apparently a npn 2222A transistor - see https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/Speed-FAN-CPU/td-p...

Alternatively perhaps the fan in the PSU needs changing?  Other than at the initial idle speed it has a really grating sound.  If possible, I might as well change it while at it?

[rcddk]

Replaced the sensor, made no difference.

I now recorded the noise on my phone:

0:00 recording starts

0:03 server is switched on - you can hear a small click.  At this time the fans are running idle, but it never comes back to this level again.

0:20 the self test starts

0;30 fans running full power, it's like a rack server, very noisy

0:45 the fans start slowing down again

1:45 the fans are now about at the standard running noise level

2:00 recording ends

So first, the noise at the first 20 seconds are fine, that's really what I had hoped to accomplish.  The noise after the self test has completed is still way too much noise. I can live with it for a moment, but sitting next to this noise more than a minute or two gives tinnitus and is annoying.  This is of course a server, and I can easily manage it remotely - only problem is I live in an apartment and have nowhere else to put it where it would be less annoying. 

With the original sensor it would spin down way faster, about as fast as it spun up. I don't know why this has changed. I used an NPN 2222A transistor as suggested. 

I ask again, is it not possible to change the fan in the PSU?  I have repaired lots of PSU's in my time, but I can't seem to get this 600W HP PSU opened. What's the catch?  Surely others must have had this problem?

[rcddk · Accepted solution]

In the end I replaced the back chassis fan with a Noctua NF-A9 PWM low-noise fan, directly mounted on the chassis, i.e. removed both the original fan and plastic box as well as the memory fan.   It is now perfectly quiet.   The problem must have been vibrations from the back case fan, amplified by the plastic box.  The memory, as previously explained, has it's own heat sink so probably will be fine without active cooling.   Only problem is that the BIOS halts on boot, complaining that it does't see the memory fan, but I guess I'll just have to live with that, unless someone can offer a suggestion.