Replacing z820 rear case fans with regular 4-pin pwm fans

[Sivoba]

That is exactly what is was looking for, thank you very much!

[SDH]

There are a few mistakes in the linked pinouts for fans as you may have noted.  For one.... the 5 pin heatsink fan's pinout has pin 5 as Tach.... there actually is a ground jumper from pin 1 to pin 5 that is present if the heatsink/fan is the larger "Performance" type (as these heatsinks are).  On many of the other HP workstations there is also a smaller "Mainstream" heatsink/fan for cooler running processors, and in that case there is no ground jumper wire, and pin 5 has not connection (but the same 5-pin connector is used).

The 6-pin plug pinout looks right.  The second pin is the 12VDC source for each of the two rear case fans..... but note that Noctua puts a limit on the wattage they want you to run through one of their resistor adapters.... rather than putting one resistor in that line before it splits to the two fans you'd want to use two resistors after the split, so each fan's 12VDC line has its own resistor individually in-line.

Personally I'd use two resistors (harvested from two of those RC7 adapters) rather than from the RC6 adapters, to try it out with lesser drop in voltage as a result.  Using a sharp strong pointed instrument you can flatten down the thin silver tab that locks that wire #2 into socket #2 of the 6-pin white plastic plug on the end of that set of wires.  This might make it easier for you to solder in the two resistors.  I gently elevate that tab back up just a bit before I reinsert it back into the plug.  That tab needs to be up a bit to lock back in place.

[muze]

---

@SDH wrote:

Well, if you're lucky someone turned the PWM fan speeds up in BIOS and all you'll have to do is turn that back down to the lowest setting.  It is easy to find in BIOS.  Most of us keep that at the lowest  value.  Some turn it up for very processor intensive projects and then turn it back down when done.  Maybe the prior owner forgot to set that back to baseline.

---

Hi SDH,

I finally got round to checking the bios, it is in it's lowest setting.

So that means I need to use the RC6 for the front and rear case fans, is there a link for any instructions on how to do that?

[DGroves]

taking the time to read this thread, and your service manual, or googling will enlighten you

keep in mind that the hp fans are matched to the system and are custom RPM/CFM designs, 

the stock fans are very quiet ( i know as i have the z800/z820 systems) and there is really no reasion to replace the

working stock hp fans. doing so can actually make the system run hotter and noiser

without seeming to be rude, your request  appears to be from someone who has little knowledge and perhaps should

not be doing this since as i said there is no good reasion for doing so,.. cutting or connecting the wrong wire(s) can cause

major damage to the system  that will cost several hundered dollars to repair 

[muze]

Thanks for your input.

The fan noise is not quiet, maybe we all have our own ideal what quiet should be.

Is there even a way to tell the fans might need replacing?

[DGroves]

fans generaly need replacing when they either fail to spin or spin slowly or make noise

i had a z800 with a bad motherboard sensor circuit (replacing the pwr cable w/temp sensor did not fix) and had to use

5 watt, 85 ohm resistors on the front/rear/memory fans to get them spinning aprox 20% faster than the stock speed

(used a strobe tach on my z820 to determine default fan speed) and the z800 system is still rather quiest

i would recomend you do what i did buy spare fan(s) off ebay for when one of yours fails and keep factory parts

i don't have a sound meter, but i know the mech drives in the case make more noise than all of the fans do!!

[muze]

Wow you have a very quiet workstation!

Sadly mine is far from quiet:(

I feel the only option left is to put the RC6's in.

[DGroves]

before you do that why not try pulling the rear fan plug starting the system and simply run a mic from a cell phone

or a headset that has a mike pluged in, and simply run a program to activate the mike, then place it in front/back and both sides while watching a audio program that has a vu meter and check the displayed noise with/without the fan running

then do the same for the front fan, the with both front fans disconnected

i'd be willing to bet it shows anmost no audio level change!!!

[SDH]

Here's a new idea:

It turns out that there are two sets of different fans for the rear dual case fans for the Z820.  These are both sets of two 92x92 mm fans that are thinner than the more common 25mm thick fans, and each has the same type of wiring as HP uses on the Z600/Z800/Z620 rear dual case fans (8 wires total, reduced to 6 total at the plug end).  I believe from the fan labels that they are 12mm thick.  They all have the same 6-pin plug ends and are interchangable.

One set for the Z820 uses Delta 0.60A fans and the other set uses Nidec 0.35A fans.  Each of these sets also can be placed in the black plastic dual fan holder used in the Z600, and then mounted in the Z600 that way.  They are simply screwed onto the rear of the Z820 as a pair, but a plastic fan holder is not used in that case.

I have bought a pair of the Nidec, new, for a test in one of my Z600s where I can use HWMonitor to measure the fan speed of the original Delta 0.60A fans that came with it versus the Nidec 0.35A..... the fans should run slower and quieter with the Nidec ones.

Rather than take all the time and effort to solder in two of the Noctua LNA resistors I'll try this first and get back to the forum here with the results.  There is a seller on eBay who currently has these pairs of Nidec fans from HP, new, if you want to search there for "Z820 rear case fans".

You can always make case fans quieter, but you don't want them so quiet that they can't do their job.  So, use a utility such as the free version of HWMonitor to watch temperatures if you experiment like this.....

[SDH]

Short answer:  Did not help.

Longer answer:  The "bonded" dual 92x92x25 mm rear case fans used in the Z600 and the Z820 (and I'm assuming also in the Z620) all are wired the same.  The fans are normal 25.4 mm thick, not some thin variant I first thought.  All wires from both fans go straight to the 6-pin white plug, and pin 1 is for the two ground wires while pin 2 is for the two 12V DC wires also bonded together at the plug socket.  Then comes pin 3 and 4 for the RPM sense and PWM control for 1 of the 2 fans.  Then comes pins 5 and 6 for the same for the second fan.

As a result HWMonitor.com can see and report RPMs for each of the two rear case fans in a Z600.  That free utility does not work for the fan speeds for the ZX20 series.

The original .6A delta Z600 rear case fans and the two versions for the Z820 (.6A Delta and 0.35A Nidec) all run virtually at the same RPMs in the Z600..... so no solution to getting slower quieter rear case fans via Nidec.

Two separate Noctua RC7 resistors (one for each fo the two 12V DC wires coming to pin 2 of the 6 pin plug) woudl be the solution to your question.  Personally I'd hesitate to use the RC6 resistors because they might slow the rear case fans too much.  Also, make sure you use a front "PCI" case fan.  Not all workstations came with that installed, but you can add one on after the fact.