Confirmation of dead PSU  

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thekaj
(@thekaj)
New Member

I've got an email in to support on this, but while I wait for a response, I wanted to check to see if there's any advice on troubleshooting my printer.

I just received my new i3MK3S+ kit on Monday, and had it doing the first test prints on Tuesday.  I was still dialing in the Z height, but otherwise it was printing fine.  I turned it off after a print, and decided to move it closer to my PC to see if the firmware needed updating.  That's when I discovered it wouldn't power up.  I discovered that the fuse in the PSU had blown, so I ordered new ones that arrived yesterday.  Put one in, and still no joy.  Things I've tested already:

  • Checked the fuses on the Einsy.  They're all fine.
  • Double-checked that the new PSU fuse is okay, and seated properly.
  • Checked all the power wires between the PSU and Einsy.
  • Plugged the printer into my computer and it mounted fine.
  • Found that the green light on the PSU does not illuminate.
  • Tested the power cord with a multimeter and confirmed it was working.  Also tried different outlets with no difference.
  • Checked the outputs on the PSU, and found NO voltage coming out of either one.

I'm guessing the last one is the clearest indicator of a dead PSU, but are there any other thoughts on other things to check?  Thank you.

Posted : 08/04/2021 7:20 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member

@thekaj

I gather thats the glass fuse next to the power lead plug you replaced?  Double check its the right type.

Would also check your cable runs just in case the insulation is broken somewhere and shorting to ground, some of the cable routes are tight going under the extrusion, make sure the zip ties are not too tight as well.

You are quicker using the chat on the eshop, will get through in 5 mins...its 24/7

Tank you very much!...
Posted : 08/04/2021 10:03 pm
Dan Rogers
(@dan-rogers)
Honorable Member

So ... new build.  Fries the fuse on power up.  I'd start by rechecking all of the 24 v connections - make sure that the lugs are not screwed in at an angle and + is touching back.

Turn off, unplug.  Take the 4 24 volt wires off of the PS so the PS is not connected to anything.  Replace blown fuse.  Plug in, turn on.  Does the fuse blow?

If the answer is no, you have a wiring short in one of those 24 volt feeds.  Trace each one back to the other end.  Make sure the lugs are not screwed in crooked and shorting out.   

If that all checks out, with machine off and unplugged, unplug all of the wires from the Einsy board.  Obtain a plug diagram for the Einsy board.  Plug everything in taking care to put the right wire to the right location.

Check the connections between Einsy and the Bed.  Are the lugs touching the other pad or each other on either end?

 

Posted : 08/04/2021 10:26 pm
thekaj
(@thekaj)
New Member

@clarmrrsn

That's right, the fuse next to the plug.  And poop.  I had double-checked the fuse type before, but on triple-checking just now, I see that I bought the slow fuses for the older PSU, rather than the fast fuses.  😣 I suppose that despite the fact that they're the same size and for the same voltage, those DON'T work, even though it looks like it hasn't blown when I put them in.

I have been testing the connectors without the wires attached to the PSU, just to eliminate the potential for there to be an issue further down the line causing the problem.

And good to know about the chat!  Thanks!  I've been looking to see where I could find it, but hadn't thought to look in the eshop.  I did get a response to my email though.

Posted : 08/04/2021 10:29 pm
Clarmrrsn
(@clarmrrsn)
Honorable Member

@thekaj

Those glass fuses have caught me out before, so many types (amp ratings and fast/slow blows)  and its rather hard to see the markings.

I keep a full kit of glass fuses from amazon for spares, have had the HiFi power amp fuse go for no apparent reason.

Tank you very much!...
Posted : 08/04/2021 10:59 pm
thekaj
(@thekaj)
New Member

Someone else reminded me that if I have a multimeter, it's trivial to actually test the fuses.  So I did a test of the original fuse, and it's actually perfectly fine.  Once I realized that it's supposed to be opaque, I didn't think it looked blown.  So I'm at a situation where I've got the PSU detached from the board, with the correct and functional fuse installed, and plugged in to a cord that definitely is providing the proper power, but there's no volts coming out of the outputs, and no green light.

Posted : 09/04/2021 12:47 am
Clarmrrsn
(@clarmrrsn)
Honorable Member

@thekaj

Seems definate the psu is toast.

Prusa chat should send you another with no problems

Tank you very much!...
Posted : 09/04/2021 10:30 am
Neophyl
(@neophyl)
Famed Member

One thing to check is that the IEC power lead is fully inserted.  From what I remember on the builds I did in the past is that they were very tight and you really had to force the plug in.  If its not actually connected then there wouldnt be any power.

Posted : 09/04/2021 10:38 am
Clarmrrsn
(@clarmrrsn)
Honorable Member

@neophyl

Good point.

My kettle lead is REALLY tight, requires qiute a bit of pressure and wiggling to seat correctly.

Tank you very much!...
Posted : 09/04/2021 10:45 am
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