Heated Bed Problem

Discussion in 'Calibration, Help, and Troubleshooting' started by 69charger, Mar 5, 2016.

  1. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Almost killed my replacement Rumba again. I am pretty sure at this point I'm dealing with a defective heated bed. Getting tired of this...
    .[​IMG]
     
  2. Chase.Wichert

    Chase.Wichert Well-Known Member

    Joined:
    Mar 1, 2016
    Messages:
    774
    Likes Received:
    207
    I'm thinking mine might be defective as well, it's measuring almost 4x the ohms as someone else's and doesn't heat properly... The glass only gets to 65c
     
  3. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Gregory, here's how it's wired. Correct polarity at the power supply as well.

    [​IMG]
     
  4. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    How do I test the bed with a multi-meter to make sure it's good?
     
  5. Chase.Wichert

    Chase.Wichert Well-Known Member

    Joined:
    Mar 1, 2016
    Messages:
    774
    Likes Received:
    207
    I tested the ohms by unhooking the bed from the rumba the just testing black and red wires, the. I unplugged the connector from the bed and tested those three sets of connectors.

    For amperage, I disconnected the red wire from the rumba, clamped the red wire to the black lead of the multimeter, and put the red probe from the multimeter on the screw of the positive connector on the rumba. Then turned it on.

    For voltage, all you need to do while the bed is heating, is put the multimeter on the red and black screw heads on the rumba, and you should get 24v
     
  6. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Ok bed resistance is 1.7ohms and voltage straight out of the bed terminals without the bed hooked up while heating is 24.4v, when not heating it is 0.00v.
     
  7. Chase.Wichert

    Chase.Wichert Well-Known Member

    Joined:
    Mar 1, 2016
    Messages:
    774
    Likes Received:
    207
    Yeah I'm not sure, Mike Kelly has been helping me and we haven't fixed my bed so, I can't tell you what it should be..
     
  8. Chase.Wichert

    Chase.Wichert Well-Known Member

    Joined:
    Mar 1, 2016
    Messages:
    774
    Likes Received:
    207
    Looks like Mike said in a post it should be about 2.7 ohms
     
  9. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Good news is it is 1.7ohms direct from the board and also when read from the end of the harness, so I don't think it's the harness.
     
  10. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Both leads from the power supply also read 24.4v
     
  11. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Limiting bed power to 1/2 or "127" will be a must for me if I ever get this working again...
     
  12. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Decided to try it again... This time I limited max bed power to 50% via firmware. Hopefully that will prevent further damage. So far so good with the bed holding 60C for about 30 min.
     
  13. Mike Kelly

    Mike Kelly Volunteer

    Joined:
    Mar 7, 2014
    Messages:
    444
    Likes Received:
    89
    1.7 ohms is a problem and will pull more current. Might explain why you're blowing polyfuses. Triple check all your connections to ensure everything is connected correctly
     
  14. elmoret

    elmoret Administrator

    Joined:
    Mar 1, 2014
    Messages:
    586
    Likes Received:
    91
    Cheap multimeters can't measure low resistances very well. If its not a Fluke or similar, I wouldn't put too much stock in the resistance measurement - could be off by an ohm, certainly.

    Better bet is to measure the current, though most multimeters top out at 10 amps which is about what the bed draws - yours may be drawing more. If you do have a 10A multimeter, power the bed from 12 volts. It should draw 5 amps when cold.
     
  15. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    As always, E3D customer service shines through. New bed, harness and Rumba on the way. I'll make sure to measure voltages and resistances before I do any heavy work. Catriona deserves a raise :)
     
  16. Chase.Wichert

    Chase.Wichert Well-Known Member

    Joined:
    Mar 1, 2016
    Messages:
    774
    Likes Received:
    207
    Hmmm, I wonder when they will get to my email to get my bed sent out...
     
  17. Chase.Wichert

    Chase.Wichert Well-Known Member

    Joined:
    Mar 1, 2016
    Messages:
    774
    Likes Received:
    207
    What email did you use to contact them?
     
  18. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    Should say I still plan to limit max bed temp to less than 100% just as a safety measure.
     
  19. 69charger

    69charger Active Member

    Joined:
    Sep 5, 2015
    Messages:
    29
    Likes Received:
    4
    BigBox Support <support@bigbox-3d.com>
     
  20. Chase.Wichert

    Chase.Wichert Well-Known Member

    Joined:
    Mar 1, 2016
    Messages:
    774
    Likes Received:
    207
    Okay, that is what I used... Thanks
     

Share This Page