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I just swapped out my MicroSwiss direct-drive extruder and hotend for a Creality Sprite Pro on my Ender 3 with an upgraded mother board to the BigTreeTech Octopus v1.1 and I'm experiencing thermal runaway on power-on.

Previous (working) configuration:

  • Ender 3 pro
  • BigTreeTech Octopus v1.1 loaded with Klipper firmware
  • MicroSwiss direct-drive

New configuration:

  • Ender 3 pro
  • BigTreeTech Octopus v1.1 loaded with klipper firmware
  • Creality Sprite Pro

Steps that I'm taking to hit thermal runaway:

  1. Turn on power switch for the Ender 3 Pro.

NOTE: Thermal Runaway Protection does not work here. The TRP detects and triggers, but Klipper doesn't seem to have any ability to control the heating tube. Instead, Klipper shuts down and the heating tube keeps running away. Each time I've had to cut the power manually.

Additional things that I've tried:

  • Powering on using the power from the Raspberry Pi's USB port - this powers on the printer but will error on any attempt to drive motors or run the extruder. RESULT: thermal runaway to the best that it can, plateauing around 60 °C.
  • Powering on using the power from the Raspberry Pi's USB port, then disconnecting and powering on without the Raspberry Pi connected, then powering down and reconnecting the Raspberry Pi - this confirms for me that in the absence of the Raspberry Pi, it still reaches a runaway state; RESULT: monitoring before and after powering manually showed a jump of 100 °C in 30 seconds, meaning if the printer has power, it will power the heating tube with as much as it can.
  • Reversing the + and - wires - this is the recommendation in the instruction manual, "If 3D printer restarts during hotend heating up, please reverse the heating tube connectors on mainboard"; RESULT: prevents the printer from powering on - everything appears dead and returning the cables to the correct polarities returns it to a runaway state.
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    $\begingroup$ sounds like your board is toast. $\endgroup$
    – Trish
    Apr 3, 2023 at 20:44
  • $\begingroup$ You are right. I swapped back in the original heating tube and it had the same issue. I was able to get it all working by using the second heating element port on the Octopus board. $\endgroup$
    – Bobby
    Apr 4, 2023 at 4:24
  • $\begingroup$ That sounds like an answer! Please post your answer and accept the answer! $\endgroup$
    – 0scar
    May 5, 2023 at 4:25

2 Answers 2

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Totally unexpected behavior?!

A heater cartridge is nothing but a resistor. Swapping the "polarity" should do nothing. As this results in totally different results, it is to be expected that the motherboard sustained damage in some area and would need a total refurbishment or replacement.

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This question seems to be solved, this (community) answer is posted as a whole from comment until the OP adds a more detailed answer.


I swapped back in the original heating tube and it had the same issue. I was able to get it all working by using the second heating element port on the Octopus board.

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