Heatbed stopped heating up, issue persists after heatbed replacement
 
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Heatbed stopped heating up, issue persists after heatbed replacement  

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arnoldwpeter
(@arnoldwpeter)
Active Member
Heatbed stopped heating up, issue persists after heatbed replacement

a week or two ago in the middle of a print my printer stopped and said that the bed had a thermal runaway, and then would not heat up afterwards. The bed still could sense changes in ambient temperature and changed with my room temperature. I checked and everything was still connected so I assumed I just had to replace the entire heatbed and that must be where the issue is. Bought the replacement kit from prusa, powered the printer up and still no heatbed heating. Checked all screws and everything is okay in the einsy, all polarity seems to be correct. The red LED does not come on for where the cables connect to the heat bed, and I do not think they were turning on before bed replacement either. A bit confused as to what the issue could be at this point. Could the entire Einsy board be fried or something? I bought this as an assembled version straight from prusa and this is really the only issue ive had so far that seems to be a genuine printer fault. 

Posted : 11/05/2022 8:51 am
Neophyl
(@neophyl)
Famed Member
RE:

First thing to have checked was the fuse on the einsy for the heatbed. https://help.prusa3d.com/article/blown-fuse-mk3-mk3s_1925

 

Fuse F3 btw

Posted : 11/05/2022 9:21 am
cwbullet
(@cwbullet)
RE: Heatbed stopped heating up, issue persists after heatbed replacement

I would also check the wires to make sure one is not broken.  

--------------------
Chuck H
3D Printer Review Blog

Posted : 11/05/2022 6:07 pm
arnoldwpeter
(@arnoldwpeter)
Active Member
Topic starter answered:
RE: Heatbed stopped heating up, issue persists after heatbed replacement

Just checked the f3 fuse. was hoping that this would be the issue but visually it is okay and multimeter verifies continuity.

Posted : 13/05/2022 9:07 pm
arnoldwpeter
(@arnoldwpeter)
Active Member
Topic starter answered:
RE: Heatbed stopped heating up, issue persists after heatbed replacement

which wires do you think i should check? 

Posted : 13/05/2022 9:08 pm
arnoldwpeter
(@arnoldwpeter)
Active Member
Topic starter answered:
RE: Heatbed stopped heating up, issue persists after heatbed replacement

Continuity is good for power from the psu to the einsy, as well as einsy to the heatbed for heatbed and thermistor

Posted : 13/05/2022 9:22 pm
arnoldwpeter
(@arnoldwpeter)
Active Member
Topic starter answered:
RE: Heatbed stopped heating up, issue persists after heatbed replacement

Just checked continuity of cables from psu to heat bed, it appears that the negative cables for both thermistor and heater are continuous all the way from the psu to the heat bed, but neither of the negative cables from the psu to the thermistor nor heater are continuous.

 

I am measuring this at the terminal of the PSU and the terminal of the einsy board.

Posted : 13/05/2022 9:27 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Heatbed stopped heating up, issue persists after heatbed replacement

Have you checked the heating bed thermistor and the wires connecting it? A defective thermistor or a bad connection can cause a thermal runaway.

wbr,

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.

Posted : 13/05/2022 9:48 pm
arnoldwpeter
(@arnoldwpeter)
Active Member
Topic starter answered:
RE: Heatbed stopped heating up, issue persists after heatbed replacement

Here is what I have done so far:

  • replaced heat bed, thermistor, and bed heater. (with this kit)
  • triple checked orientation of positive/negative cables
  • checked bed heater terminals for damage
  • checked continuity of einsy to heat bed 
    • Positive and negative are continuous
  • checked continuity of f3 fuse
    • continuous
  • checked continuity of all PSU to Einsy cables
    • all positive and negative are continuous
  • checked resistance of thermistor and bed heater
    • in expected range
  • checked continuity from PSU terminals to heatbed terminals
    • negatives are continuous, positives are not continuous
  • Red LED on printbed also does not light up when it is supposed to
Posted : 13/05/2022 10:06 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Heatbed stopped heating up, issue persists after heatbed replacement

If the mechanics are okay so far, a factory reset and a firmware reflash may help.On the other hand, the Einsy Rambo may be causing the problem. I would forward this to the Prusachat.

wbr,

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.

Posted : 16/05/2022 5:28 pm
JoanTabb
(@joantabb)
Moderator
RE: Heatbed stopped heating up, issue persists after heatbed replacement

did you replace the heatbed power wires, with the new ones from the kit? 

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 : 16/05/2022 5:59 pm
Zoltan
(@zoltan)
Moderator
RE: Heatbed stopped heating up, issue persists after heatbed replacement

Your power transistor feeding the heatbed cartridge could be gone if youndo not see the bed connector red light flashing. Are you on the warranty? If so contact support ASAP. If not, to contact them could be useful, they can advice you.

even an old man can learn new things 🙂
Standard I3 mk3s, FW 3.10.1 RC1, MMU2S, no closed box, Fusion 360, PrusaSlicer, Windows 10
PRUSA MINI FW 4.3.4, Prusa Connect Beta

Posted : 20/05/2022 6:57 am
Zoltan
(@zoltan)
Moderator
RE: Heatbed stopped heating up, issue persists after heatbed replacement

Btw. You can check your old bed by ohmmeter if it is shortcut or broken. The regular resistance should be AFAIK around 12 - 16 Ohms for 24V and 40W 

even an old man can learn new things 🙂
Standard I3 mk3s, FW 3.10.1 RC1, MMU2S, no closed box, Fusion 360, PrusaSlicer, Windows 10
PRUSA MINI FW 4.3.4, Prusa Connect Beta

Posted : 20/05/2022 7:02 am
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Heatbed stopped heating up, issue persists after heatbed replacement

allow a small correction:

MK3/S/+ Bed

voltage =24

max. current about 7 ampere

max. power about 170 watts

resistance about 3.5 ohms

wbr,

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.

Posted : 20/05/2022 7:25 pm
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