Hotend Not Heating/Incorrect Resistance
Hey All,
I got my MKIIS last week, and while I successfully printed a few things, today I had a failed print due to a runaway error. After testing for a bit, with trying both to preheat, as well as manually set the hotend temperature, the temperature would not change from an ambient of ~31C. After looking around for fixes, I dug into the circuit to try to isolate the cause.
First off: There is a voltage across the hotend resistor wires on the Rambo board. The thermistor seems to be correctly seated on the Rambo pins, and the hotend power terminal on the Rambo end seems to be correct seated. Nothing else is malfunctioning, like logic/hotbed/Screen, so while I haven't checked the fuse, it doesn't seem likely.
The problem seems to be, when I measure the resistance across the hotend resistor itself, either from the Rambo terminal connector, or from the exposed wires near the resistor, I get a resistance of ~560kOhms. Apparently, that should be only around 6-7Ohms... so, am I stuck with going and replacing the hotend resistor, or is there anything else I obviously missed? It seems like this is a such a rare problem I haven't seen any suggested fixes of it elsewhere.
Thank you,
Sean
Re: Hotend Not Heating/Incorrect Resistance
Did your meter actually show a negative Ohms?
Re: Hotend Not Heating/Incorrect Resistance
Nah, that's a tilde ~. Both of temperature and resistance numbers are approximate.
Anyway, just a quick update. I ended up ordering some heater cartridges via amazon to replace it. I suspect the leads going into the heater cartridge got pulled out just enough to lose the connection. Next time I will be sure to secure the extruder wires a bit better.
Edit: I was going to point out there was one other oddity with the extruder, once I took it apart. I don't know if it's normal or not, but the grub screw on the aluminum heater block was overtightened so much that the heater block itself was bent. I am still trying to get it out, after accidentally stripping it, but I may have to try to cut a slot into it to remove it.
Edit 2: I just realize a tilde looks correct when editing a comment, but looks like a - when displayed. Odd.
Re: Hotend Not Heating/Incorrect Resistance
May I ask how you got the grub screw out? I have to replace my thermistor and the grub screw doesn't want to budge and it's a bit stripped at this point. I have no idea how to get it out now.