1 Topic by thebestebahn

  • thebestebahn
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Topic: Temperature stuck at -20C...help!?

To begin, I bought a second-hand printer and I've been trying to set it up to work. I've already flashed the Repetier firmware and I have full functionality of the machine (i.e. I can raise the bed temperature, move in all axes, and heat the extruder). The problem that I have is that from the moment I turn on the printer it reads that the extruder temperature is -20C. Whether I heat it up or not the temperature doesn't change. Here's what I've tried:

>Checked the room temperature resistance and performance of the thermistor when heating...everything normal
>Followed the circuit from the thermistor to the mainboard while searching for any discontinuities...couldn't find any
>Checked the resistors at the socket on the main board to see if any were blown...all where normal
>Directly connected the leads of the thermistor to the connector that leads to the main board and bypassed the small circuit board..same issue
>Checked the Repetier Firmware settings in the configuration.h file to see if I had messed something up. A friend from afar suggested some changes but nothing related to the thermistor. I've tried a number of different thermistor types and tables to see if any of them would work...the initial temperature of -20 will change depending on the table but doesn't move (i.e. same behavior)

So right now I need some ideas. Something to look into that could be the culprit. I've been looking into a grounding issue but I'm not sure how the grounding should work in a properly working machine. I have continuity from most of the motherboard and components to the frame of the machine but strangely only one side of the thermistor has continuity to the frame. If someone could verify this that would at least take out one possibility but any ideas or help is greatly appreciated. Thanks.

2 Reply by carl_m1968

  • carl_m1968
  • carl_m1968
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Re: Temperature stuck at -20C...help!?

Are either of the thermistor leads exposed and touching the brass heat block?

Printing since 2009 and still love it!
Anycubic 4MAX best $225 ever invested.
Voxelabs Proxima SLA. 6 inch 2k Mono LCD.
Anycubic Predator, massive Delta machine. 450 x 370 print envelope.

3 Reply by thebestebahn

  • thebestebahn
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Re: Temperature stuck at -20C...help!?

Hello, I just checked and the sleeves seem to be in place. I did not see any continuity between the heating block and either of the thermistor leads. I've also checked with a thermistor that is outside of the printer area so there is no risk of shorting at that location.

4 Reply by thebestebahn

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Re: Temperature stuck at -20C...help!?

bump for some help!

5 Reply by carl_m1968

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Re: Temperature stuck at -20C...help!?

If the thermistor measures around 100k at room temp and changes as it is heated then your issue is in the mainboard. I am going to guess the AD converter is fried. Logically -20 is a direct short across the thermistor or the the output of the the AD converter that coverts the analog value of the thermistor to a digital value and sends that to the processor is dead. There are no schematics for this board so you would have to follow the traces. There should be an IC between the thermistor input and the processor on the board. That IC is most likely your issue.

Printing since 2009 and still love it!
Anycubic 4MAX best $225 ever invested.
Voxelabs Proxima SLA. 6 inch 2k Mono LCD.
Anycubic Predator, massive Delta machine. 450 x 370 print envelope.

6 Reply by thebestebahn

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Re: Temperature stuck at -20C...help!?

Thanks for the suggestion. I haven't found an IC that seems to be sending out unexpected measurements but that's hard to diagnose everything. I've been out of town and now that I'm back I'm going to return to this project. I emailed XYZ printing regarding the possibility of purchasing a replacement motherboard outside of warranty. If anyone knows where I can buy one from somewhere else that would be greatly appreciated. I am also considering just switching to a different platform such as RAMPS or a SmoothieBoard to save me the headache of finding a new motherboard. Any more suggestions appreciated! Thanks.