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Solved Err: MAXTEMP BED

Discussion in 'Troubleshooting' started by Mark Gandenberger, Mar 19, 2018.

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  1. Mark Gandenberger

    Mark Gandenberger New Member

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    So, I had just finished one print and was getting ready to start a second when I got a MAXTEMP BED error. The bed temp reads 233. The temperature stays the same even with the bed cable unplugged at the board. I have also tried a backup bed and there is still no change to the temp. So, here are my questions:

    1) Am I correct in thinking this is likely due to a Ramps board failure?
    2) If the Ramps needs replacing does it make sense to go ahead and switch to a generic?
    3) Are there any recommendations for good replacement option or versions to avoid?

    Thanks
     
    #1 Mark Gandenberger, Mar 19, 2018
  2. Geof

    Geof Volunteer Moderator
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    Yes sounds like a ramps failure (thermistor selection shorted) if unplugged the bed shows the same and a new bed plugged in shows the same.

    I personally think its worth swapping to a generic if you are able to relocate some wires, do some stripping and trimming etc. If that makes you uncomfortable reach out to robo for a R1+ direct replacement (they are the only ones who have them, and may not be in stock? no idea)

    I just buy from amazon. Get a few, if ones bad, return it.
     
    #2 Geof, Mar 19, 2018
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  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Given the cost of the generic ones... I am with @Geof -- buy a few. I have gotten them Prime and had free returns on a bad one :) Still less than $15
     
    #3 mark tomlinson, Mar 19, 2018
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  4. Geof

    Geof Volunteer Moderator
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    I think of the 10 or so I've got from various vendors (testing out the vendors for the thread Mark and I made on converting) only 2 were bad. Prime let me return at no cost :D
     
    #4 Geof, Mar 19, 2018
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  5. Mark Gandenberger

    Mark Gandenberger New Member

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    Thanks! Robo has the Ramps+Arduino for $100 and that seemed pretty expensive for the convenience of drop-in replacement, especially if it's unlikely this will be the last Ramps I ever replace. Sounds like a generic is the way to go.
     
    #5 Mark Gandenberger, Mar 19, 2018
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  6. Geof

    Geof Volunteer Moderator
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    yep been around that price since release (one of the main reasons we did the thread). Just outrageous when compared to a generic. You can buy a ramps, arduino, stepper drivers (jumpers included as are heatsinks), LCD controller and wires as a kit for around 40.00
     
    #6 Geof, Mar 19, 2018
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  7. Mark Gandenberger

    Mark Gandenberger New Member

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    Well, my new Ramps board(s) arrived today so I immediately got working on installing a new one. I had everything but the fans and LEDs hooked up so I thought I would turn the printer on to make sure I didn't have anything wired incorrectly. Lo and behold, I'm still getting bed temp error, even with the thermistor disconnected. The only conclusion I can make is that it's my Arduino board that's bad rather than the Ramps. Is there something else I might be missing?
     
    #7 Mark Gandenberger, Mar 20, 2018
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Assuming I am reading it correctly and you haven't omitted anything egregious :)
    I agree... However, eliminate the wiring by reading the resistance from the wires at the RAMPS back to the thermistor itself. Should be ball-park 100k ohms.
     
    #8 mark tomlinson, Mar 21, 2018
  9. Mark Gandenberger

    Mark Gandenberger New Member

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    I don't think I've left anything out but that's why I figured it would be good to double check my thought process. In my mind there are only 3 possible culprits - the RAMPS, the Arduino and the thermistor. I had ruled out the thermistor because I still got the overtemp (233C) even with it disconnected, rather than the 0C that I expected. I also tried plugging it into the extruder thermistor location on the board and it read properly there. Taking your suggestion, I just now checked its resistance and it reads 92.8K ohms. I've got a new Arduino coming tomorrow so hopefully that fixes the problem. Until then, does it sound unusual for the Arduino to fail, rather than the RAMPS? I'm also trying to figure out if the failure could have somehow been caused by my doing. Is there anything potentially problematic with periodically removing the bed to clean it? I didn't think heater and thermistor connections would be particularly sensitive.
     
    #9 Mark Gandenberger, Mar 21, 2018
  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    And the wiring/connections, but let's lump that in with the thermistor :)
     
    #10 mark tomlinson, Mar 21, 2018
  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The RAMPS is the usual suspect when I/O failures occur, but it is not unheard of for the Arduino to go bad (and when you are talking an Analog input port it is even less unusual).
     
    #11 mark tomlinson, Mar 21, 2018
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Nope, that is totally fine as long as you are not doing anything silly I would not expect this to cause failures.

    The ugly "Secret" is that this printer uses commodity electronics (which is why you can buy the entire lot of electronic guts, for < $50 in a kit, on Amazon). Commodity parts are exactly that... they can die :) Last time I went in to troubleshoot a stepper driver that was bad (and it was) the RAMPS and the Arduino died as well. Bear in mind that they do NOT use actual branded Arduino Mega 2560 units, but made in China clones.
     
    #12 mark tomlinson, Mar 21, 2018
  13. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The Good news out of all of this is :


    :)
     
    #13 mark tomlinson, Mar 21, 2018
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  14. Mark Gandenberger

    Mark Gandenberger New Member

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    Well, after enduring one more setback (my new board delivered to somebody a couple houses up the street) I finally was able to install a new Arduino and that seems to have taken care of my maxtemp error on the bed. So, to summarize:

    1) printer would not print, due to MAXTEMP BED error (bed temp was reading 233C, even with bed disconnected)
    2) RAMPS board was likely suspect, since bed wiring and thermistor tested fine
    3) installed new generic RAMPS board but it did not solve the problem
    4) installed new Arduino and now everything seems to be functioning properly

    Thanks again for all of the help!
     
    #14 Mark Gandenberger, Mar 22, 2018
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