Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)  

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

Hi Caleb, 

Do you have a voltmeter to test the powersupply output,?

do you have more than one fuse on the input side, perhaps one in the plug as well as one in the powersupply?

I believe there is also a fuse, inside the powersupply, if you feel qualified you could open the powersupply and test that fuse too! 

regards Joan

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

Hi Joan,

I do have a voltmeter, so I can test the power supply output. I found this: https://help.prusa3d.com/article/mvzxcjkvtx-troubleshooting-multimeter-usage   What should I be testing in particular?

I did rule out the outlet as the problem by testing other devices in the same outlet.

As far as opening the powersupply to replace a fuse, I'm sure it's not a big deal, but I've never done it before.

Testing the output of the PS seems like the best route for now. I will post back when I do that. Thanks for the help!

Caleb

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

I measured the voltage output from the PSU (measuring DC voltage on the two fork terminals) and I didn't get anything.

If I'm not confident messing with the inside of the PSU, what are my next steps?

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

@caleb

Hi Caleb,

I would make sure all of the power leads going to the einsy were disconnected and safe (insulated),

then try plugging a known working  IEC lead, into the power supply and see if the voltage comes on when you turn the switch on...  

If it works OK try the old cable again... if the old still doesnt work, your cable is duff, 

if your psu doesn't work with the new cable either, then your PSU is probably duff...  have a word with Prusa Support

the powersupply for a mk3 is in the eshop, but you have to login to see it!

Joan

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

there are 4  24 volt terminals, did you test a +positive one, to, a -Negative one?

Joan

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

Since you are at this point in testing - I would disconnect all the cables from the PSU. Mark which one goes where.

Now see if you get voltage. That will tell you if the PSU or power cord is bad or one of your outputs is shorted.

The PSU should crowbar if it sees a short, independent of fuses blowing.

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

When a PS fuse pops, it usually indicates a failure within the power supply, not an overload.   But, you can test to see if is is an overload by removing all the wires at the PS end. Power up the PS and measure the +24 to -24 junction screws.  If there is 24v, it might be the Einsy board has failed.  Or it may still be the PS.  

But, 5A and 120v is over 600 watts ... the power supply turns off when load power exceeds about 250-300 watts.  It is unlikely the Einsy caused the failure.  So testing the power supply should be done carefully as there may be a grounds fault failure, and exposed surfaces are now live 120v AC.  Caps, transformers and inductors, and internal heatsinks are also subject to being at elevated voltages; but with a fault, normally safe points can be elevated and unsafe to touch.  Proceed testing with extreme caution.

ps: I've probably been lax in using the crowbar term, but there is a difference.  A power supply will crowbar (in some cases) when an over-voltage condition occurs and if it has a crowbar circuit (a designed failsafe for mission critical applications where an overvoltage will cause catastrophic damage).  Normally, the PS in the MK3 simply shut down the inverter during overvoltage and overcurrent conditions.  

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

@joantabb I tested the the positive and negative fork terminals as shown here:

I did not remove the wires from the PSU, I removed the terminals from the Einsy board and tested those. I also tested another power cable to the wall with no difference.

I can test the screw terminals of the PSU directly, with no wires plugged in as you guys have suggested.

I see the power supplies in the store now that I've logged in. Thanks for that information. I will contact support once I test the PSU directly.

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

@caleb

Cheers Caleb,  just checking. 

good luck.

did you find out what caused the original fuse to blow?

regards

 Joan

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

Thanks for the help everyone. I bought a new PSU and the printer works now.

RE: Printer won't turn on, replacing blown power supply fuse doesn't help (MK3)

which one did you buy Caleb?

Regards Joan