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Need Help - Thermal Runaway  

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Teriaki
(@teriaki)
Active Member
Need Help - Thermal Runaway

So the easiest way to explain what's going on is to start from the beginning.

Currently running a Prusa MK3S

a few months ago I started having some issues with some plastics where it would under extrude, other plastics were fine so I chalked it up to just the certain plastic not being very good.

At some point, it started under-extruding and while I was trying to troubleshoot what was going on it stopped extruding at all.
It had been a while since I had replaced any of the parts so I replaced the nozzle in hopes that would help
Same issue.
Then I thought I might as well replace the entire hotend heatsink and all and while were dismantling the hotend the heater just came right off its wires which had become frayed during the nearly 3 years of use and i guess were holding on by a thread.

So I order and replace the heater and things work for a few minutes until the heater suddenly won't heat up anymore.

seems like I got a 12V 24W heater instead of a 24V 40W heater that I ordered, so I assume the heater got too much voltage and popped (there was a brief smell, but I didn't think at the time as it didn't smell like electrical burn to me)

So I order another heater and make sure after It arrives that it is marked as 24V and 40W and install it
To my pain, the same things happen, no smell, but the heat will not heat up.

The build plate WILL still get up to temperature like normal, it is just the hotend that won't heat up and throws a TEMPERATURE RUNAWAY error after a few seconds when preheating in any way.

Does anyone have any ideas on a fix or what component might need to be replaced, because I'm completely lost now.  I have been pulling my hair out for months, and just want one clean print at this point...

Any help would be wildly appreciated.

Posted : 21/07/2021 1:57 am
JoanTabb
(@joantabb)
Moderator
Unexpected results.

seems like I got a 12V 24W heater instead of a 24V 40W heater that I ordered, so I assume the heater got too much voltage and popped (there was a brief smell, but I didn't think at the time as it didn't smell like electrical burn to me)

So I order another heater and make sure after It arrives that it is marked as 24V and 40W and install it
To my pain, the same things happen, no smell, but the heat will not heat up.

Hi Teriaki. 
12 volt 24 watt heater?  seems an odd value. 
could it have been a 12 volt 40 watt heater? 

either way, a 12 volt heater is not a good idea, on a 24 volt system

if you install a 12 volt heater on a 24 volt   system, you end up drawing (or trying to draw) 4 times the expected power from the circuit

the Einsy controller has three fuses fitted, 

https://help.prusa3d.com/en/article/blown-fuse-mk3-mk3s-mk3s_1925/

Fuse 2 is rated at 5 amps and I believe it feeds the extruder heater. this may have blown. 
alternatively, the mosfet on your einsy may have blown, or the heater power connector on your einsy board may have over heated and melted. 

I hope these pointers will help you, 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 21/07/2021 4:58 am
Teriaki
(@teriaki)
Active Member
Topic starter answered:
Will need to look into these.

Whoops, yes I meant to type 12V 40W for what I recieved.

 

So it sounds like take the einsy out and see any of those three are damages/scorched or melted and replace them.

Hopefully it's not too catastrofic In terms of damage.

Is there a good place to source replacment parts like these? (I don't really want to run the risk of getting different parts than ordered again)

Posted : 21/07/2021 5:41 am
Teriaki
(@teriaki)
Active Member
Topic starter answered:
Will need to look into these.

Whoops, yes I meant to type 12V 40W for what I recieved.

 

So it sounds like take the einsy out and see any of those three are damages/scorched or melted and replace them.

Hopefully it's not too catastrofic In terms of damage.

Is there a good place to source replacment parts like these? (I don't really want to run the risk of getting different parts than ordered again)

Posted : 21/07/2021 5:41 am
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