Anycubic I3 Mega S - Thermister Replacement

If any of you guys ran into this issue as well this is how you replace the thermistor in you’re heated bed.
Video Tutorial

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@Yarkspiri that is a really nice video beautifully done!

Alex

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Thank you. It was pretty hard to come by a tutorial on this, so I decided to make one just in case someone else ended up needing it.

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yes the bed wiring on those is atrocious they always fail I’ve seen over 20 of them in the shop with the same issue you just need to replace the thermostat some of them have actually had to replace all the bed wiring as well just make sure you get the right strain relief on there in the correct wiring when you replace it

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Are you the one that actually did the video? If so, I have to question whether you were taking the resistance readings with the bed (and thermistor) plugged in (not turned on, mind you, just plugged in).

In that case the “strange readings” that were mentioned are the result of the thermistor being in parallel with the input impedance of the measuring circuit on the motherboard. To get a proper reading, the thermistor must be disconnected.

Alternatively, if the board/thermistor was disconnected, you would have to take into account the temperature coefficient of that particular model of thermistor. Some of them can be quite high, and even a few degrees off the nominal 25C temperature at which they are rated will result in a reading that can be 10s of thousands of ohms off from the 100Kohm specified at 25C.

Otherwise, good video.

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Yes I actually did make the video myself. The machine was plugged in and turned on I believe. I followed the same steps as when updating my stepper motors which was definitely incorrect from the looks of it. I appreciate the information since it’ll definitely be useful to me in the future.

If you have time to copy and paste this within the comments of the YouTube video, I’ll be able to pin it for other viewers. It’s very good information and I would prefer that people also know who provided the information.

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The follow-up video was actually the rewiring of the connection hub which fixed the problem. That video should be live sometime latter today. And boy was that a hassle.

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For heavens sake, don’t take resistance measurements with the power turned on. The internal battery of the ohm meter is what supplies the power for the measurement.

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Well now I know. I appreciate the info.