Synology DS411+II fan swap πŸ› 

Since I wanted to update/replace the fans on my NAS, I thought I’d document the work made, with some additional information for anyone attempting, and hopefully succeeding in swapping their fans on the DS411+II and similair models!

How it looked before, after, and a heads up πŸ›‘

Before After

This is the stock configuration, the fans installed are as follows:

  • EC4010M12ER 40x40x10 mm (CPU fan)
  • KDE1208PKV3 80x80x20 mm (case fans)

Problem is: All of those, including alternative models, are usually extremely expensive or unobtanium.πŸ’Έ

But fear not, for I have something to tell you! 😼

🚨ALL of those fans are rotor-lock type fans, meaning they share the +12 V and GND pins of common PC fans, but they DO NOT HAVE A TACHOMETRIC/RPM SIGNAL OUTPUT , instead they have a ROTOR LOCK DETECTION OUTPUT.🚨

This means if you want to know when your fans are fucked: DON’T JUST REPLACE THEM WITH NORMAL FANS!

How to replace the fans and keep rotor lock detection πŸ‘€

So, you want to use the usual fans, but don’t wanna lose rotor lock detection? I’ve got just the thing for you!

Here you can find the forum thread I based my design off of:

Materials: πŸ›’

  • 1x any 3-pin (VCC,GND,TACHO/RPM) 40x40x10 fan
  • 2x any 3-pin (VCC,GND,TACHO/RPM) 80x80x20/25 fan (not over 25mm thick!)
  • 3x 33k resistor (0.25W will do just fine!)
  • 3x any diode (I used 1N4007 AFAIK)
  • 3x 47uF/16V electrolytic capacitors
  • 3x any NPN small signal transistor (BC547 or BC337 work fine!)
  • 3x small screw terminals with 3 contacts (optional)
  • 3x small lengths of heat shrink tubing (around the board)
  • 3x stripboard pieces, approx 15x3 holes in size

Model and maker of those fans are up to you, I personally chose Noctua fans, as they’re super quiet and reliable, if a tad more expensive then usual PC fans.

If you want a recommendation, here’s what I used:

  • 2x Noctua NF-A8 ULN (80x80x25)
  • 1x Noctua NF-A4x10 FLX (40x40x10)

Schematic ⚑


This schematic is based off the link above, changes are:

  • Rearranged for better understanding
  • Q1 swapped for BC337 (Which I had on hand!)

If you’ve really read this far down, I will assume that you have a basic understanding of electronics and are attempting to build this magical contraption!

Here’s an incredibly low resolution image of my finished board: Board

Other bits and bobs πŸ€Έβ€β™€οΈπŸ›ΆπŸ¬

  1. Don’t use case fans over 25 mm thick, they 100% will not fit. Believe me, I’ve tried! On the next pic you can see the clearence between the HDD cages and the fans when the case is closed, it’s there but…🀏 barely! Fan gap

  2. I highly recommend the screw terminals, they allow you to swap the fans a lot easier, and you don’t have to solder every time you swap the fans πŸ‘ˆπŸ‘ˆ

  3. Take care with your cable management, stuff it where the fans and HDDs are not. This seems obvious until you shove the trays back in and DSM reports that 3/4 disks are connected…πŸ˜…

  4. The CPU fan connector is not a standard 3-pin PC fan connector. Either you solder the old connector onto the new one, or you do it like I did it: Screw terminals ☝ Connectors

  5. You cannot screw the fans to the outside of the case, due to the fan grill being bulged (owo) outwards. Bulge