Power Supply failure  

Re: Power Supply failure

This thread does have me concerned, hope someone at Prusa can at least assure people that the clicking sound is normal.

BTW, I don't think PRPZ-24-240 is the model number, sounds more like a label for Prusa. If you look through the top back of the PSU with a flash light you can see the manufacture on the board. My unit says T-LED with a model number and what appears to be a version TLPZ-24-240 v2. Would be interesting to see if people have different versions, especially those who have clicking sound vs those who don't.

I could be wrong I believe this is the link to the company/power supply, makes sense as they are in CZ, the T-Led logo matches as does the yellow inspected sticker 🙂

https://www.t-led.cz/p/led-zdroj-24v-240w-vnitrni-5525

That would be strange as the PSU supposed to be something like 90-264V and not being switched between 90-132V and 180-264V by hand, like the MK2/s PSUs are.

I think it's a variation, none the less, logo on the board matches T-Led...

Re: Power Supply failure

Can we please stop focusing on the CE mark and focus on the clicking/potential PSU issue. Its already been established that that CE mark matches China Export....check Page 6 of the handbook for product details.

Re: Power Supply failure

I agree that the thread does not apply to the CE mark.
But it is important that manufacturers respect the meaning and design of the CE mark.
There is a reason why CE logo is ready to download in different file formats.

Manufacturers must certify that the product complies with the directives that apply to the product and is safe to use.
It is punishable to use the CE logo if you do not comply with the directive as stated in its declaration.

As an example, the Swedish Electrical Safety Authority has tested 60 different USB chargers.
14 of them were so dangerous that they were charged with a sale ban and must be revoked.
Most of these chargers were provided with different misleading marking, CE included.

Re: Power Supply failure

I agree that the thread does not apply to the CE mark.
But it is important that manufacturers respect the meaning and design of the CE mark.
There is a reason why CE logo is ready to download in different file formats.

Manufacturers must certify that the product complies with the directives that apply to the product and is safe to use.
It is punishable to use the CE logo if you do not comply with the directive as stated in its declaration.

As an example, the Swedish Electrical Safety Authority has tested 60 different USB chargers.
14 of them were so dangerous that they were charged with a sale ban and must be revoked.
Most of these chargers were provided with different misleading marking, CE included.

Thus why the manual marking encompasses the entire printer vs the maketings on the parts. So lets get back to focusing on if there was a bad batch of PSUs or if everything is ok.

Re: Power Supply failure

Couldn't agree more Joe but how do we determine this ?

I guess some detective work is needed, mine's going under the microscope for sure but how to verify the build quality and component standards without taking one apart ?

Could do with a failed one that won't nullify any warranty when taken apart.

The current seems low to me - is that RMS or peak, constant load or max permitted, it doesn't say neither on the PSU nor does the printer documentation, in fact I haven't seen any details power consumption details. Is it +24 and -24 or +24 and circuit ground (not necessarily earth referenced ground). It would help a lot if such things could be communicated, reluctance to communicate such things only says one thing to me.

A 'typical' stepper motor can draw 1.5 amps peak and there are 5 of them - that doesn't leave a whole lot of headroom from 10A for power hungry heaters - and PSU's should generally be derated by 50% for reliability so that would mean this PSU is too small i.e. a 10A max load would require a 15A PSU. Then there is the Einsy recommendation for a 16A PSU ...

Designed and assembled in USA by UltiMachine.

Firmware / Hardware Information -
Recommended Power supply 12V-28V DC, 16A+.

draw your own conclusions ...

Re: Power Supply failure

I picked up a new PSU since it takes forever for Prusa shipments to get to me. I grabbed a 350 watt unit as I totally agree that 10A is not enough. I think someone dropped the ball on design here or was trying to improve the bottom line. But when you get deep into a 30 hour print the PSU if undersized will most likely pass away.

Re: Power Supply failure

Well, all 4 steppers indeed can consume such current, but those are spikes and you can't (don't need) to assume that you need to have 5A reserved just for steppers. Quick spikes can draw some of the current from reservoir capacitors.
Second - they never draw full current all 4 simultaneously, but more or less only two of them (x and y).
Third, steppers work when only bed and nozzle are already heated, so those two don't draw full current anymore. As such i guess 240W is enough, but i agree that they could give some more reserve to it.

I would measure primary current (at 230V side), but i'm just in the middle of the print. I'll do it later and get back.

Re: Power Supply failure

Primary current won't necessarily tell you what the load is trying to pull, either way it states 3.6A but is that constant or max there's just no information, depending on the caps installed I'm betting the inrush current is huge, I'd be interested to see a log of the 24V current during a 'typical' print cycle, something took this thermistor out, the prime candidate for that is excessive switching (as in constantly charging and discharging capacitors - inrush current - sometimes heard as clicking / popping .... ) or simply too much current.

Re: Power Supply failure

MK3 has independent CE testing from AKPtesting. It is attached. We have CE certificates from T-led for the PSUs too. They made all the PSUs for MK2, so they are pretty reliable. Please let us investigate and cooperate with the support. We did our homework before the release.

Re: Power Supply failure

Prusa Research just contact me stating they believe the power supply took a surge and that is the cause of the failure. To which my response was:

"I don't see how the power supply would have received a surge. Our home is on totally clean conditioned power supplied through 42 solar panels. The power then passes through an inverter and then battery backup system with power conditioners. I will review the power conditioner data in a graph. Historically over the past 6 years the power has been 100% clean. And even still the electronics around here are plugged into surge protectors as well. I think your devs are barking up the wrong tree here."

The failure also happened when we were on 100% solar power and not power company.. I Just don't see it being a surge.

Re: Power Supply failure

Nice to hear from you Jo, good stuff to know, such things aren't clear in the available documentation i.e. power ratings etc. Would be nice to have a detailed 'tec spec' section in the docs for the geeky types.

Re: Power Supply failure

MK3 has independent CE testing from AKPtesting. It is attached. We have CE certificates from T-led for the PSUs too. They made all the PSUs for MK2, so they are pretty reliable. Please let us investigate and cooperate with the support. We did our homework before the release.

Jo, is there a valid technical reason as to why the PSUs are making noises? Are they safe?

I initially cancelled my order because of this thread and then reconsidered. My wife said that I should keep my order and I have confidence in your customer service team because they did a wonderful job for me.

Re: Power Supply failure

I connected power meter to printer, so here are results for PLA, nozzle 220, bed 60 degrees:
When heating up from cold, it draws around 270W, 280VA, cosfi is very near 1.00, at aroung 0.96.
When it's heated up and printing power consumption is around 50-70W at cosfi around 0.50 - 0.60. So, PSU unit is maxed only when heating up. 270W at around 80-90% efficiency is just around 240W.

Re: Power Supply failure

Says to me there's not enough headroom - the PSU should NEVER be maxed in a good design ... so perhaps this warm up needs to be staggered in some way to avoid stressing components. Many people print much hotter than that - not everyone uses PLA - I'm mostly ABS / PETG and Nylon ...

Suggestion - heat up the nozzle - hold it there then heat the bed but don't do both together from cold.

Re: Power Supply failure

I agree that PSU is too maxed out. However, i think this might be very simple to solve: in printer settings - start g code switch two lines - from
M115 U3.1.1-RC4 ; tell printer latest fw version
M83 ; extruder relative mode
M104 S[first_layer_temperature] ; set extruder temp
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp

to
M115 U3.1.1-RC4 ; tell printer latest fw version
M83 ; extruder relative mode
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M104 S[first_layer_temperature] ; set extruder temp


This way bed will be heated first, when it's up nozzle will start to heat (at least i understand this code this way).

EDIT: Maybe better way is to use M109 instead of M104 for nozzle heating in first code, this way nozzle would heat first.Second code is not OK because printing will start before extruder is hot!

Re: Power Supply failure

Sounds like a plan ... don't think it really matters who goes first.

Re: Power Supply failure

Watch out my mark in previous post - i made an error. In second code use of M109 is a must, or printer will start to print cold...
So, i guess it's more simple just to alter M104 to M109.
Not sure, but i think that S3D have separate heatings by default...

Re: Power Supply failure

As for the heating of the hotend and bed separately. That is how Cura is doing it for my clone printer and uses these commands the following order:
M190 S50
M104 S200
M109 S200

So first the headbed heats up and waits for that, then sets the hotend temperature and waits for it to reach the temp.

As for the power supply, i expect my mk3 in March, and by then i think problems will be sorted out, but i can understand all concerns here. So will continue to read all the developments.

Re: Power Supply failure

Decided to look at some of the gcode produced by Slicr and it seems to have an erroneous M104 immediately after the set bed and wait so is the firmware obeying M190 ? - it is definitely doing almost as suggested and inserting the M109 though.

M107 ; fan off
M190 S80 ; set bed temperature and wait for it to be reached
M104 S235 ; set temperature
G28 ; home all axes
G1 Z5 F5000 ; lift nozzle

; Filament gcode

M109 S235 ; set temperature and wait for it to be reached

I suppose you could use M117 and some text immediately after the M190 and then an M226 to see if it does 'wait', if the text appears before the bed is at temperature you know that it isn't waiting, I'll look into why Slicr is adding the M104 in any case.

I looked at the gcode from the latest Slicr and it comes out like this which if I'm reading it right will enable both together

M104 S230 ; set extruder temp
M140 S85 ; set bed temp
M190 S85 ; wait for bed temp
M109 S230 ; wait for extruder temp

Same order that it appears in the custom gcode settings in Slicr on the printer tab so I guess that's where to change.

Re: Power Supply failure

I feel the heat bed should go first as it takes the longest to reach its temperature. The nozzle heats up in little time.

Give Prusa time to take a look at it and work it out.