Hotend not heating - Pinout Main Cable
I get a hotend error while calibrating. The hotend doesn't warm up at all. The hotend is within Ohm range so that's OK. And the thermistor reacts correctly when I'm warming it up with a hot air gun. The fuses are OK. The black plug gives 0V so I'm guessing/hoping there is a break in the main cable. Everything else seems OK.
Is there a pinout table or something like that somewhere so I can do a continuity check on the cable?
RE: Hotend not heating - Pinout Main Cable
Check for a blown fuse? The Core One uses the same xBuddy board.
RE: Hotend not heating - Pinout Main Cable
All the fuses are OK
RE: Hotend not heating - Pinout Main Cable
On the Prusa OpenSource page (I find it by clicking the gray Open-source button on the left half of the drop-down when you click on "Company" at the top of any Prusa web page) there are links to the schematics for both the Love Board and the xBuddy Board. The Love Board is only one page and the connector appears to be at schematic coordinates C-7. The xBuddy schematic is 18 pages long, but the connector for the Love Board is on page 11 (Extruder) at schematic coordinates A/B-5. I haven't looked carefully enough at both schematics to see if the cable is 1-1 or if some pins get swapped.
Good luck with your troubleshooting.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: Hotend not heating - Pinout Main Cable
Thanx a BIIG bunch. This is exactly what I needed! 🙂
RE:
I just went through this on my MK4S (pretty much the same Nextruder). This was the cause:
I must have been too rough with this connector (which is the heatbreak thermistor). Oddly, the outside metal mounts for 2 of the connectors are tied to the +24V trace rather than ground. I don't know how long that trace was delaminated, but halfway through a print it broke (probably due to vibration). Took a while to diagnose, but Prusa support quickly narrowed it down to the Loveboard. Ordered a new one and I'm back in business.
The diagnostic steps were to measure the resistance of both the heater and thermistor (both OK), set the temp etc. In my case it was always reading near room temperature, and so was the heatbreak. PS said if it was the main cable, there would be other error codes (I don't know what those would be though).
Prusa MK4 since Jan 2024, MK4S/MMU3 since Jan 2025, Printables: @MikeB_1505898
RE: Hotend not heating - Pinout Main Cable
It's VERY plausible that I managed to do something similar! Thanx a BIG bunch for the comprehensive answer!
RE: Hotend not heating - Pinout Main Cable
As I swap nozzles by swapping the full nozzle assembly, I often connect and disconnect that thermistor. I've found a technique for disconnecting that helps me with my fat fingers. I use an Allen key (the 2.5? mm ball end one that I keep near the printer for checking that most screws stay tight and adjusting the extruder tension) to depress the locking tab from the side and then the cable slides easily out of the board-mount connector. I find that this technique helps me reduce the wear and tear on the connectors for me.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs