Suspected Power Supply Unit Failure + Replacement with Meanwell LRS-350-24 Issues
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Suspected Power Supply Unit Failure + Replacement with Meanwell LRS-350-24 Issues  

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Suspected Power Supply Unit Failure + Replacement with Meanwell LRS-350-24 Issues

Hello everyone!


I’m in a little situation here, I’ve had my Prusa i3 Mk3 since November 2018, and it served me well up to Dec 2019. From then, the screen started flickering during powering up, and then completely not turning on. 


I suspected it to be a power supply failure (but could not confirm it as the fuse was not broken). Therefore, I decided to get a common replacement supply unit: the LRS-350-24 after reading: (this one was for the RSP-350-24, but for the wiring I followed this one extensively)

And the main  prusa manual :


As I couldn’t print the housing for the PSU without the printer first working, I thought it was worth going ahead and assembling it in this really, raw way. However, when I turned on the power supply, it did nothing.  I then adjusted the male end of the wire that connected the power outlet to the female socket(that of the PSU cause it seemed loose (pictured), and it short circuited and I got mildly shocked. I know this is really unsafe practice, but I checked it many times to ensure that it was wired properly. Therefore, would anyone with similar experiences with their prusas not turning on, know if it is: A wiring error, Wrong power supply,  Something missing, or something else is wrong with my prusa, or something else entirely? I have a multimeter, would that help in identifying something?

^ wiring I followed with credits to  jonathan-r14 

Any help/suggestions for this noob would be appreciated! 🙂 

* I apologize if I am unclear, I will provide more details if I missed anything 

* I also apologize for the masking tape, it was to label the wires 


^ where I adjusted which caused it to short circuit, did not touch the exposed wires or anything! 

Posted : 26/03/2020 5:26 pm
Active Member
RE: Suspected Power Supply Unit Failure + Replacement with Meanwell LRS-350-24 Issues

Two things.

First - there's a switch on the side of the power supply, along with a warning sticker. Make sure that's switched to the correct voltage to your supply - either 115v or 230v. Obviously, ensure that you're completely unplugged before you do that.

Second - once that's done, or if that's done already, hook it back up and grab a multimeter to check for power. Making sure that your multimeter is set to AC current, and being extremely careful, touch the black tip to N and the red to L. You should see the relevant voltage coming in from the mains. If not, then a problem exists between the wall and the PSU. (Likely the glass fuse) If so, then change the multimeter to DC current, and touch the black tip to one of the v- pads, and the red to the v+. Should show 24v. If not, your power supply is likely dead from that short and you'll need to order another. If it IS showing 24v, and you're wired up correctly, then your PSU is providing the correct power to your Einsy, and the fault lies there. Disconnect, and check the automotive blade fuses on the Einsy board - both 5A and the 15A.

Posted : 02/04/2020 6:34 pm