Is my bed dead ? Can I fix it with a 2.5 upgrade ?
 
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Is my bed dead ? Can I fix it with a 2.5 upgrade ?  

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olivier.l
(@olivier-l)
Active Member
Is my bed dead ? Can I fix it with a 2.5 upgrade ?

Hi

I have a problem with my heatbed : my print stopped with a bed thermal runaway.
I have a domino between the bed and the rambo. This domino was completly melted. I've already had a melted connector so I thought it was the same problem and I just changed the domino after checking that the connector on the rambo side was OK.
Then, when I tried to heat the bed, nothing happend so there is a problem 🙁

- I unplugged the domino and tested the voltage out of the rambo : it is OK, I have 11,8V
- I checked the 1K SMD resistor near the status LED, and it is OK
- with the bed not connected to the rambo I checked the resistance beetween GND and VCC and I found 1 Ohm. Seems quite low to me. I fear that the bed is shorted and will no longer work.

What is going on here ? is my bed dead ? Is there some additionnal tests that I could make on my bed ?

If the bed is dead, maybe it is time to replace it during a 2.5 upgrade, given that I have a problem with a broken wire on my PINDA too that I fixed temporarily by soldering a piece of wire. Are the 2.5 upgrades available for shipping ? I don't want to wait 4 month to fix my printer 🙁

Thank you for your thoughts on my problem.

Veröffentlicht : 08/03/2018 7:04 pm
Nikolai
(@nikolai)
Noble Member
Re: Is my bed dead ? Can I fix it with a 2.5 upgrade ?

I would suggest contact the Online Chat Support. They will guide you through the check list.
In general if you have a molten part, then you have a shortage somewhere. Replace the cables to the heat bed and do the measurement again

Often linked posts:
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Veröffentlicht : 08/03/2018 8:08 pm
olivier.l
(@olivier-l)
Active Member
Themenstarter answered:
Re: Is my bed dead ? Can I fix it with a 2.5 upgrade ?

the cables between the bed and the rambo are ok. do you know what resistance I should have between vcc and gnd ?

Veröffentlicht : 08/03/2018 8:35 pm
digibluh
(@digibluh)
Reputable Member
Re: Is my bed dead ? Can I fix it with a 2.5 upgrade ?


the cables between the bed and the rambo are ok. do you know what resistance I should have between vcc and gnd ?

it's a heater, 1 ohm is what it should be. less than that like 0.5 could be a bad thing. thermistor should be 100K, if it's wrong it could try to pull more power. but seems this is a common thing due to the connectors itself. it could be loose and not making 100% contact and melting while not drawing enough current to blow the fuse. you could add an external FET board to offload the current from the rambo board like:
https://www.banggood.com/3D-Printer-Parts-Board-High-Power-Expansion-Add-on-Heated-Bed-MOS-Module-p-1141753.html?rmmds=search&cur_warehouse=CN or solder them directly to the board, swap for a different connector like bullet connector types.

See: https://help.prusa3d.com/l/en/article/VcWVlvvjg7-heatbed-not-heating-up-properly

Veröffentlicht : 09/03/2018 3:19 am
Calire
(@calire)
Honorable Member
Re: Is my bed dead ? Can I fix it with a 2.5 upgrade ?

At first : think that it is a big current through the heating bed. so don't mount a tiny domino. Look at the size of cable and take a good size for the domino ; and thighten strong.

Veröffentlicht : 10/03/2018 10:31 am
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