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Solved 91.3 degrees print bed even when off

Discussion in 'Troubleshooting' started by gunsmoke132, Mar 20, 2018.

  1. gunsmoke132

    gunsmoke132 Member

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    for some reason, my print bed is reeding 91.3-91.4 when I turn it on. iv reset it unplugged it and it still reads 91.3
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Bad therrmistor most likely, but bad wiring/connections TO the thermistor can do that and lastly (and least likely) a bad RAMPS board.
     
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  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    If it reads the same with the thermistor physically disconnected from the RAMPS board then... you have a bad RAMPS :(
    I don't think Robo still has stock replacements for the R1+ (the R1 used standard ones) but call them to be sure.

    If not you can use this thread to replace it with a (cheap) standard RAMPS 1.4:

    Ramps redo in R1+:
    http://community.robo3d.com/index.p...and-rewiring-to-make-generic-ramps-work.8356/
     
  4. gunsmoke132

    gunsmoke132 Member

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    id make sense... I accidentally shorted the thermistor on the heater block. what kind of heating pad should i buy if that's the issue and is it possible that i killed the thermistor and the ramps? because I'm not getting a reading on the thermistor and when i plugged in a 100k ohm thermistor in the temp didn't change
     
    #4 gunsmoke132, Mar 20, 2018
    Last edited: Mar 20, 2018
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    It is probably not the thermistor itself if it does not change when disconnected. It is probably the wiring or the RAMPS board.
    The heating pad on the bed is also probably just fine (it is a big-old resistor itself and hard to kill).

    Just be clear exactly what symptoms you have -- as I understand it the bed temperature is what is not reading correctly :)
     
  6. gunsmoke132

    gunsmoke132 Member

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    i tested the thermistor on the heating pad for resistance won't give a value (only shows "OL")
    also, the value for temperature is unphased by whether or not the thermistor is plugged in but the "temp" is now 80
    also when plugging in a spare thermistor it is unphased
    if something on the ramps were to fry what do you think it would be? like could i quickly solder something up and replace it.
     
  7. Kilrah

    Kilrah Well-Known Member

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    If you connected the thermistor input to heater power you'll have fried the analog input (possibly more) of the atmega2560 chip.
     
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  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I'd go with possibly more. :)

    So bad thermistor for sure as long as you were on a range of the meter that could handle 100k ohms. Also I assume you mean the thermistor, not the bed heater. The bed heater is at best a dozen ohms or so normally unless it is bad and in that case you really need to call Robo since I do not know of an exact replacement for that part (there are others that can replace it, but we already have some threads on that you can refer to)

    ...and that sure sounds like a bad RAMPS too. Sadly these things often come in bunches (dead parts). Not sure exactly what all you have at the moment, certainly a bad thermistor, maybe a bad RAMPS, maybe a bad Arduino and maybe a bad bed heater? Test all of these things carefully... document exactly what steps you took.

    I usually suggest people buy one of the kits on Amazon that has all of the parts and use that for spares. Again with an R1+ you will need to review the thread I already linked to earlier since it is not a DROP-IN for the RAMPS. This link goes to an example only (I am not recommending this specific store/product) there are a number like this on Amazon, find one you want and you can have all of the electronics handy:

    https://www.amazon.com/OSOYOO-Printer-Controller-Stepper-Heatsink/dp/B0111ZSS2O
     
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  9. gunsmoke132

    gunsmoke132 Member

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    no more. just the Arduino. I bought both just in case (plus I plan on building a printer so extra parts will eventually be consumed) and tested everything out and the RAMPS board is fine ;)
     
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  10. gunsmoke132

    gunsmoke132 Member

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    i think its fixed. it turned out to be the arduino. :)
     
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  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Thanks for closing the loop on that, helps others troubleshoot.
    I would have suspected the Arduino since it was an analog, but it does route through the RAMPS so I couldn't just rule it out :)
     

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