Power Supply failure  

Re: Power Supply failure

So I dug a bit deeper... The issue with the clicking and the PSU is a bad thermistor NTC 5D-11. It failed rather violently with flames and everything. Thermistors are known to making clicking noises when they are not functioning properly. Leading to a failure and usually a blown fuse, which I have as well.. I've opened a ticket with Prusa.

Re: Power Supply failure

Interesting...A clicking PSU just before the bed reaches temp seems to be a common issue. Mine ticks right before the bed reaches temp, but not during prints.

Re: Power Supply failure

NTC is not a supplier.
NTC stands for Negative Temperature Coefficient.

It's a thermistor issue.
Maybe this is the issue that is holding up shipment in the past week, as told by a support representative? Or a new one? Who knows...

Re: Power Supply failure

Would you mind posting a few pictures of the failure?

Re: Power Supply failure

I contacted support about the clicking of the power supply on my MK3 while the heat bed is heating.

"The clicking noise is not a concern at all. It does not harm the PSU at any way and will be taken care of in future FW updates."

I wonder how they will fix the PSU thru a firmware update. And now I'm a little worried after hearing about a PSU failure.

I guess it's something to be aware of.

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They will adjust the heatbed PWM frequency and resolution in firmware to stop that clicking.

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Here are pics from the failed power supply. When it failed there was a flash of fire from inside the case. The printer had been printing for almost 70 hours when this happened.

The first pic is the blown thermistor. there may be other parts that let out the magic smoke as well.

The second pic is the chunk of thermistor that fell out of the PSU case.

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Thanks for posting pictures, this really concerns me. I lost a house, animals, and everything I own to an electrical fire. These wide spread PSU issues have been really concerning. I think at this point I'll cancel my order and buy the MK2S.

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Cancel order? Well...in MK2S power supply is very similar, only that it's 12V. So noone can guarantee you that it won't "explode". These PUS?s are all pretty much similar built, so it can happen or it can't happen, regardless of model...
Don't cancel just because of this issue. I understand your fear, but in your place i would rather put some fire/smoke detectors in room where printer is located.

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I appreciate it but I cancelled the order and went MK2S anyway. I'll buy the upgrade kit when the bugs get resolved. The lack of communication or acknowledgment has been a huge issue for me.

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It does make one wonder just what sort of build quality these PSU's have - there is some real junk coming out of China - not everything is of course but the presence of the CE mark on Chinese stuff means nothing unless you've seen the cert since it is quite often marked but not legitimately. There have been numerous reports of vibration and clicking.

Even if it is CE marked is the power supply underated for what is being expected of it (since testing doesn't test this).

Thermistors as regulators aren't ideal and are prone to thermal runaway. If the current through an NTC thermistor is too high it gets too hot, the hotter it gets the more its resistance decreases, this causes more and more current to flow, which increases the temperature still further and is known as thermal runaway which only ends in one of two scenarios - the load fries or the thermistor does. It would be interesting to see the currents on the steppers, the heated bed and the hot end at the time this blew itself apart.

I'd be interested to see a teardown of one of these PSU's to see just how well made they are and what grade of components has been used since the PSU is pretty much the heart of the machine on which everything else depends.

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If it helps any, I was printing PETG. So the bed was maintaining a 90 degree temp and the extruder at 240 for a lot of hours. The printing of a higher demand filament may have contributed to the failure.

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Even if it is CE marked is the power supply underated for what is being expected of it (since testing doesn't test this).

That CE mark on China products is not necesarilly european CE sign but often Chinese "China Export" and it's quite legal. It's also somewhat different than european sign and of course, quality is ...well...
http://www.ybw.com/vhf-marine-radio-guide/warning-dont-get-confused-between-the-ce-mark-and-the-china-export-mark-4607

Chinese are big experts in copying all kinds of stuff (like Penasonic vs. Panasonic, Germany bearings, where "Germany" is name of chinese factory, while naive buyer would think that bearings are indeed Germany (Deutsch) made...)

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When I was cancelling my order I mentioned this thread to customer service and they said they were aware of the issue and will be looking into it. Hoping the rep would talk me out of cancelling, I briefly mentioned other bugs that were bothering me and the rep said they're aware of all of the bugs and that they're working on it. That troubled me because they're aware that there are hardware bugs and they've done nothing to communicate to their customers publically. I waited 3 months for my MK3 and it was due to ship next week.

I expect bugs when it comes to new products. I can't tolerate bugs that may potentially cause a fire and hurt someone. I'll continue to actively lurk on the forums and hope that the bugs get worked out. Once they do, I'll most likely buy the MK3 or an upgrade kit.

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OK, let's be honest: there can be NO bugs allowed when it comes to simple PSU unit. Such units are widely available and used for many years, we all know (and they know, too!) that there are "chinese" and "normal" PSU's. At this price of printer there can be no such failure's as selecting "chinese" PSU instead of some recognized brand, where they (and we) can be sure that it works...
I bought many "chinese" switch PSU's in the past. But, i always knew risk i'm taking...
Quite different thing is Einsy board, if it's new...

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I'm with you on this, since the PSU is bought in the excuses are zero, providing the appropriate specification has been bought in that is, I do hope that they are taking notes and heeding them.

They seem to be but time will tell I guess, I think there was a little too much haste in the MK3 release trying to get it released for the US exhibition, perhaps the prototypes used different components, perhaps corners have been cut to get stock in by suppliers, only Jo and his people really know the answers.

I agree with corey.3d that communication needs to improve significantly, I don't think that most people would mind if there are issues providing they're kept informed, but 'we' aren't.

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Does anyone know the original part model number? Maybe we can just change it to a higher quality part ourselves which I have no issue doing. I do hear clicking while heating up and printing and it's PLA so it's not something that needs to be excessive in the heat department.

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The part number on mine is PRPZ-24-240. Made in PRC. 🙂

two days with a ticket, no response.. sigh..

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The part number isn't helping much, any known specs on it so we can get alternatives?