Why would anyone want to replace the SR’s power supply? The answer (at least for me) is Peace and Quiet.

As you know, when you turn on the SR the power supply fan starts immediately, and never shuts off until you power off the printer. Moreover, the power supply fan is quite noisy, especially when the printer is sitting right next to you. I found this noise to be quite annoying.

Several months ago I found out this does not have to be the case. There are power supplies out there who’s fan only turns on when required. And I discovered this while I was working on upgrading an old printer from a 12V power supply to a 24V one. It makes quite a difference – while I was testing I found out that the power supply fan ran only about 50% of the time and would turn itself on and off fairly frequently.

Here’s a photo of the power supply I used:

Meanwell LRS350-2

Here is a an Amazon link if you want to try the same upgrade:


Here are the steps I went through:

First, it is critical to be aware of what the various power supply electrical connections are. Getting these wrong will probably cause grievous damage to the power supply and/or the printer. Here are the power supply’s connections – the good news is they are the same for both the SR and the Meanwell:

From right to left these connections are 110V/220V Hot, 110v/220V Neutral, 110V/220V Ground, 3 24V Negative DC, 3 24V Positive. Note that, just like the SR power supply, it can be driven by either a 110V or 240V source. And just like the SR, the Meanwell has a switch on the side to select which voltage you have.

Be sure to set this switch to the correct voltage BEFORE you install it in the printer because after installation the switch is not usable. This is because the Meanwell is a thinner box than the SR and the Meanwell switch does not line up with the cutout in the side of the SR base.

Here is a photo of my SR on the operating table ready for it’s upgrade:

The bottom plate comes off easily by removing the 6 screws at the corners. The SR power supply is easily accessed:

Here is how the SR’s power supply is connected:

Again, from right to left there is the 110V/220V Hot (brown), 110v/220V Neutral (blue), 110V/220V Ground (yellow), a single 24V Negative DC (black) ,and 2 24V Positive (red). I decided to disconnect/connect the wires one by one, but to do this I had to cut and remove the tie wrap to fee up enough wire length to reach the Meanwell’s connectors.

The wire connectors for the input power require the screws to be fully removed because they are closed:

The 24V connectors only require loosening the the screws because they are open-ended, This makes it a lot easier to switch them from the SR to the Meanwell. Here are all the wires transferred to the Meanwell:

I had to revers the order of the last 2 wires because one was just barely long enough to reach the Meanwell, But this is not a problem because all the connectors in each group serve the same function.

Surprisingly the most difficult part of the conversion was mounting the Meanwell back in the SR base. Because it is thinner the Meanwell has only 2 mounting holes, so it attaches using the 2 bottom set of screw holes in the sides of the SR base. Holding the Meanwell in place and aligning the 2 holes was not nearly as simple as it sounds, so I finally decided to replace the SR’s mounting screws with longer M4 ones. This made attaching the Meanwell much easier; here it is in it’s final position:

It fits flush with the bottom lip of the SR base, and the fan opening is not in the same place as the SR one, but there are many holes in the SR base plate so I am not anticipating any problems. This is what the outside of the base looks like after mounting the Meanwell:

Note the top 2 empty screw holes, my 2 M4 screws, and the empty space for the voltage selection switch. The Meanwell sits completely below this space but it really is in there.

So what happened when turned the power on? Peace and Quiet of course. The SR screen lit up just like it always did, the touch screen controls worked just like always, and the printer is happy. The only noise is the hotend’s heat sink fan which is barely audible. I’m working on the design for a fairly long running print now and it will be interesting to see just how often the Meanwell’s fan goes on.

Last Update: 27 Jul 2021