SOLVED MINTEMP BED - RUMBA is broken?

Discussion in 'Calibration, Help, and Troubleshooting' started by SandervA, Aug 15, 2016.

  1. SandervA

    SandervA Member

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    Hey guys,

    Just when I thought I was making progress, I encountered another puzzling problem; when I start my BB-dual hybrid it displays MINTEMP BED and also both extruders are showing 0oC. When I then disconnect and reconnect the the cable for the extruder PT100s, I get the right temperature (around 23oC at the moment, which reacts to external heating of the hotend). However, the bed temperature stays 0oC. I measured the resistance of the bed sensor at the end of the cables plugging in the RUMBA; at 23oC, it is around 100-115 kohm. I measured the 2 terminals of the RUMBA board, which indeed put out 12V. Anybody got an idea what could be the issue?

    Also, when I connect both pins on the RUMBA with a 100kOhm resistor, nothing changes. Seems that my RUMBA is broken?

    Many thanks in advance,
    Sander
     
  2. tohara

    tohara Well-Known Member

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    If you measure 12v on the terminals for the bed heater thermistor there is some wrong wiring, or something wrong with the Rumba. You should only measure 5v on the THB terminals.
     
  3. SandervA

    SandervA Member

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    Hey Tohara,

    Thanks for your reply.
    These are not the dedicated THB terminals, but the ones next to EXT3, which have a 12V indication next to them. According to the build manual, these are the ones I should use. If not, then this problem is easily solved. I don't mind using the THB terminals on the side of the board, but doesn't that mean I have to change this in the firmware?

    Kind regards,
    Sander
     
  4. tohara

    tohara Well-Known Member

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    The terminal next to EXP3 marked 12v is 12v dc supply and the cover fan should be connected to this terminal.

    The thermistor should be connected to the THB terminal. That it also what the stock firmware is set up for.

    Do you have a link to where you found this in the build manual?

    Edit: The BED Thermistor should go on THB, the wiring from the PT100 should go to EXP3.
     
    #4 tohara, Aug 16, 2016
    Last edited: Aug 16, 2016
  5. SandervA

    SandervA Member

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    Dear Tohara,

    Thanks! This solved my problem; I probably should stop building my BB at night ;).

    Just another question if I may; my left Z-axis motor is only moving the platform down (right is functioning perfectly) and when moving up, it just jolts and then nothing. I checked the grub screw and the bolts holding the screw; all very tight. And if I try moving the axis by hand, the motor is also moving. I checked the connections, which seem to be fine. Also added a bit of lube to both axis, which didn't do much.

    Do you have any suggestions here?

    Many thanks in advance,
    Sander
     
  6. Dr Jeep

    Dr Jeep Well-Known Member

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    Two things here, before you do the z homing setup later on in the build, it is possible you can't move towards the home position (the firmware won't let you move an axis beyond what it thinks is the 0 point, but until autohome is working and calibrated it won't know where that 0 point really is)

    Juddering can also be due to the stepper voltages not being set right, you may find you need a bit more on the Z driver due to it having 2 motors in parallel. I think I have mine at 0.65v
     
  7. Dr Jeep

    Dr Jeep Well-Known Member

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    I'd get to the bit when you are homing Z in the build and if it still won't move up when you follow those instructions then look at the voltages.
     
  8. SandervA

    SandervA Member

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    Dear Dr Jeep (cool name btw),

    Thanks for your suggestions; in my case this didn't solve the problem. It turned out some connection in my cable was broken, even though my multimeter did not reveal this initially. I now removed the header that plugs onto the pins on the RUMBA, twisted the wires into pairs and connected via the screw-terminals. This completely solved the issue.

    So many thanks to all that helped me with these silly issues.

    Kind regards,
    Sander
     

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