HP M6720 Fan Mod

Builds DAS
1

Decided to replace two 15-bay rosewill chasis (bottom two) with a head units and disk shelves. Ended up with a Dell R720 8-bay LFF and a HP M6720.

20240215_181528
20240215_1815281920×2560 473 KB

The Dell is no louder than the Rosewill, but the HP is so loud that can be heard with the room door closed. I am thinking limiting the fan speed by adding a physical controller to all its fans.

It turns out that all the fans are in the power supply. Here is what it looks like inside the power supply.

20240215_175218
20240215_1752181920×1440 326 KB

Screws:

20240215_175506
20240215_1755061920×1440 225 KB

Model Number:

20240215_175444
20240215_1754441920×1440 193 KB

Close-ups on the fan connector: (I assumes it is two connectors for two motors integrated into a single fan housing? the other wire is the status LED on the back of the metal case)

20240215_175402
20240215_1754021920×1440 146 KB

20240215_175911
20240215_1759111920×2560 322 KB

What is the best path forward to reduce the fan speed? It is a 4-pin connector so I assume it is reporting the RPMs back to the controller and receiving PWM signal from the controller to control the RPM. If I simply reduce the fan speed, the controller will try to compensate, and it just end up running at max. Any suggestions?

2

I found a solution, by using external PWM signal generators.

20240502_225811
20240502_2258111920×2560 500 KB

20240502_225837
20240502_2258371920×1440 129 KB

They are powered by the power supply fan headers. I removed the PWM wire from the fan connector and connect it to the PWM signal generator, and use the button to control the fan speed. I can get it to below 60db at 1% and maintain all 24 drives at high 30C with ambient temp at 20C.

3

Hi there, I have the exact same problem with the thing being too loud. I bought a pwn signal generator similar to the above - would you happen to have a diagram of how you wired this up at all please? Also do you know the model of the fan/fans themselves so i can see if i can replace them with something from Noctua etc. Thanks in advance for you help, greatly appreciated!