No heating of BOTH nozzle AND bed
Hi all,
during an ABS print tonight (after about 2 h of print in a 20°C room) the Printer reported a „thermal anomaly“ and stopped printing. My diagnose so far:
- all 3 fuses are intact
- heating bed and nozzle with a hairdryer increases temperature in both, so the thermistors seem intact
- thermal calibration is not possible, it beeps and stops after a few seconds
- manually setting the nozzle temperature results in a „thermal anomaly“ error
- manually setting the heatbed temperature results in a „heatbed preheating error“. Note that there is NO red LED visible in the heatbed connector as it would be normally, so the heatbed does not get any current?
- preheating manually leads to a „thermal anomaly“ error, no printing is possible
- idle nozzle temp is 20°C, heatbed is 20°C, room temp is 27°C according to the printer (it is actually 20°C). Can the difference between real and measured room temp be the cause?
Update: I upgraded to firmware 3.14.0, but all symptoms persist.
If it was nozzle or heatbed alone I would simply try to repair/replace that, but the fact that BOTH devices fail to work (plus the fact that three is no red LED on the heatbed connector during preheat) tells me that there might be something more crucial happening (mainboard problem?).
I did not yet get an answer from Prusa, so I would appreciate any ideas or suggestions from you all ... thanks in advance!
_Melt
(PS: I did not try a factory reset yet as I would like to keep all mechanical calibrations untouched (plus I think a hardware failure seems more likely, bit I will of course try that if you think it could be helpful.)
(PPS: Printer statistics: total filament used: 700m, total print time: 12d 14h.)
[Update] No heating of BOTH nozzle AND bed
Hi all,
for those interested in this issue a little update:
After a live chat with Prusa support I made some measurements.
- Thermistor resistance heatbed: 3.3 kOhm
- Thermistor resistance nozzle/hotend: 109.0 kOhm
- Heating resistance heatbed: 3.3 Ohm
- Heating resistance hotend: 15.0 Ohm
All measurements performed at 24°C ambient temperature. According to Prusa specs for MK3S+ specifications, these values look fine to me.
But as I already suspected: there is no voltage on neither heatbed nor hotend connectors when commanding a temperature increase in the settings/temperature menu. I tried measuring directly on the connector pins on the einsy board. That fits to the observations that there is (1) no led lighting up in the heatbed connector and (2) not a single degree of temperature inclease reported by the thermistors.
I also checked the connections on the einsy board (visually and without disconnecting all the cables as I did not have the connection plan at hand), and I also looked at the visual appearance of the SMD components on the board, but I did not see anything that looks broken, loose or scorched (well, I’m not an electronics specialist though …).
While fiddling with the printer I realized something. When setting the nozzle temperature to induce heating, the printer quickly (after several seconds) runs into a temperature anomaly error and beeps. After multiple clicks on the dial selector to shut off the beeps, I realized a sound coming from the power supply unit, it sounded as if a cooling fan was active (although there is no fan in the power supply). This sound stops immediately after pressing the cancel button.
I then checked for this sound, and I realized it is always present, although normally it is a lot quieter. It is not a 50 Hz sound, my spectrum analyzer says its main frequency is around 1500Hz. And I remember that I sometimes came into the room to check for prints, and I heard this sound. But at that time I did not know there is no fan in the power supply.
Could it be that there is some broken or fading component in the power supply? The output voltage is at 23.8V, and all mechanical parts and motors are working. But maybe the heating draws so much power that the power supply cannot deliver, so the power relays do not activate the heating?
My search continues, waiting for a reply from Prusa. But if any of you has an idea I am eager to hear about it ... especially from people with a good electronic intuition and/or experience who can decide whether my theory about the power supply could be true ...
_Melt
[Update 2] No heating of BOTH nozzle AND bed
Hi,
correction to my last update: heatbed thermistor resistance was 106.6 kOhm, I copied the wrong number.
After some chats with Prusa we think that the Einsy board is the source of the error. I removed it from its cover and tried a visual inspection, but I could not identify any problems. I then re-connected everything (to rule out any connection problems), but no luck. So I decided to try a new Einsy board. I'll keep you updated as soon as it arrives.
_Melt
RE:
Yay - it works again, reliable and precise as ever!
With the new Einsy board everything is working again. What a relief ...
Thank you, Prusa support team, for the competent, friendly and supportive chats that helped to pinpoint the defective part.
(BTW, sorry for the late reply, but the Wacken festival ( 😎 ) and a Covid infection interfered with an earlier posting 😀 )