Heater problems -

Epinephrines

Hi everybody!

I recently ran into some issues with my heated bed and I hope that you can help me.
After a lot of patience and hard work I finalized my Hypercube evolution and because of the missing stealth chop on the Duet2WiFi I exchanged it and got a shiny Mini 5 plus. After the initial configuration, everything went well and I was able to get it to print for the first 100 hours. That's when the problems started:

At first, I got choppy readings from the bed thermistor, especially in the area below 40 degrees sometimes resulting in a heater fault: bed temp rising too slow (which was actually just bad readings). I then replaced the thermistor drilling a hole into the aluminum bed at the side and putting the thermistor with some thermal paste inside.

Readings where smooth now but when I tried to tune the heater with an M303 H0 S85, Phase 4 took more than 4 hours and cancelling with an M0 didn't work so I hit the emergency stop to reboot.

Now the heater won't do anything at all. Tuning results in a "no rise of temperature detected" error and I cant manually power the heater. Is it possible that I broke heater or the fuse by interrupting the auto tune?

Thanks in advance,
Epi

Phaedrux

When you moved the thermistor farther away from the heater itself you decoupled it from the heater meaning it takes a lot longer for the heat to arrive at the thermistor. This is why it took longer.

Now it sounds like the mosfet for the bed heater may have failed or the fuse. Do you have a multimeter to test with? Pull the fuse and test it for continuity first. If it's good, check the voltage on the bed heater terminals when you turn on the bed.

Epinephrines

@phaedrux Thank you very much for your kind answer.

Mystery solved: It was a bad crimp at the heater cable. Nothing to do with tuning! Checked the fuse which was perfectly fine and the output of the Board was 24.0V. Left only the bed heater as a possible problem.
Checked the resistance between both heater cables and was already worried that the heater was just broken but after removing the cable endings and checking again, there was continuity again with slight resistance. Reconnected and worked again!

Thanks again.

Epi