since i bought a new oem hotend and ive replaced it…had nothing but mcu extra errors. any help please
Hi,
Could you please tell us more ?
since ive installed the new hotend, i get on the screen of my printer extra mcu error, once underlying issue is resolved please restart firmware and im left with only 2 options , network management and restart firmware. i have put the i.p address into my laptop and have looked on the web ui (mainsall) that the klipper error is extra mcu. ive done alot of reading into how to fix this and ive got no idea since the wiring is fine there is nothing loose or broken. ive tried restarting firmware and i just keep getting the mcu extra error on the web ui. the led light comes on for one second then goes off. (the led light on the toolhead) ive used a multimeter and there is constant 24v power being used regardless of the toolhead light being on or off while the printer is on. one of the wires the ceramic heating wire seems to heat up real quickly and pretty hot. its odd because i cant actually see what temperature it is because im still stuck in the klipper error. the nozzle and everything else doesnt seem to heat up just the ceramic heater wire.
On the Max the [extra_mcu] is the toolhead board.
Probable causes:
- Improper/corrupted firmware on the toolhead MCU
- Bad CANbus wiring between the mcu and the extra MCU
- Bad CANbus hardware on either MCU
What prompted you to replace the toolhead?
The toolhead should have had the firmware when it shipped. But your’s wouldn’t be the first that had to be flashed. There is a python script that is supposed to be able to flash over CAN but the other users with DOA toolheads had to use a STlink to flash.
Get a support ticket open by sending email to info@sovol3d.com. Include the order number for your printer AND the toolhead.
I went through the terminal on my laptop (ssh) and pinpointed the fault to the ceramic heating wire . When it was shipped I seen the pins on it were back to front e.g where the left pin goes in the right pin was wired to it instead . Some reason when I did some codes through ssh (thanks to the draining chat gpt with all his safety precautions which lead me to waste hours instead of getting to the point ) every connection on the toolhead pcb seems to be alive just some error about those 2 pins with the ceramic heater wire. So gpt suggests
“Yep. In simple words:
24 V getting to the board is good. That means the board is receiving power.
Now we need to check if the board itself is making the smaller voltage the chip needs to run: about 3.3 V.
Set your multimeter to DC volts:
- Black probe on GND
- Red probe on the board’s 3.3 V point
If you get around 3.3 V, the board is powered properly and we move on to the CAN/firmware side.
If you get 0 V, the board itself likely has a power/regulator problem.
If you’re not sure where to touch the probes, send me a clear photo of the toolhead PCB and I’ll point out where to test.”
So I’ll be following that. Got a new hotend due to heat reep and other damage to the hotend
no luck ai suggest three wires from toolhead to mainboard??
There are a total of 5 wires toolhead to mainboard. They are broken out to 2 connectors.
2 wire - 24V power
3 wire - CAN bus
Pictures at:
im using st link and im eve nhacving issues connecting to the toolhead this is very frustrating
Fair warning, this might come across as blunt or even rude, and that’s not the intent. For context, I’m a maintenance lead in pharmaceutical manufacturing, so troubleshooting and teaching people how to troubleshoot is what I do all day. I took the time to read your whole thread and write this up because I’m trying to help, so please take it that way
Two things you said stood out: ChatGPT burned hours on safety precautions instead of getting to the point, and it told you three wires run from the toolhead to the mainboard. Both of those are fixable, and neither means AI can’t solve this.
“AI” isn’t one thing. It’s like saying “transportation.” Were you on a bicycle or in a lifted 4x4? A quick-answer model with no setup and a top-tier model set up to research and verify are not the same tool.
Why you got what you got:
- The safety lectures happen because it doesn’t know who it’s talking to. With no instructions, it assumes a beginner and pads everything.
- The three-wire answer was a guess. cardoc corrected it: 5 wires, 2 for 24V and 3 for CAN, straight from Sovol’s GitHub. It never checked a source because nobody told it to.
- Same with the “3.3V point.” No pinout, so it was guessing board layout.
- Meanwhile it skipped the biggest clue in your thread. The heater pins were wired backwards, and the heater gets hot while Klipper is halted, which means nothing is controlling it. Now you’re fighting an ST-Link connection to a chip that may not be alive.
How to get a real answer out of it:
1. Use the strongest model you can access (Claude, ChatGPT, Gemini, Grok, etc with my experience Claude.AI has been exceptional). Turn on extended thinking or reasoning and web search if your plan has them.
2. Set it up once. Most have a preferences or custom instructions setting. Tell it you’re hands-on, skip the safety lectures, verify hardware claims against manufacturer docs before stating them, say “I don’t know” instead of guessing, and give one step at a time. That alone fixes the wasted hours.
3. Feed it the sources. Link Sovol’s SV08MAX GitHub (the Motherboard folder has the pinouts), upload your klippy.log, and attach clear photos of the toolhead board and connectors.
4. Make it reason before it prescribes. Ask “what do these symptoms rule in or out?” before “what do I do next?”
5. Don’t let it escalate to reflashing or ST-Link until it has confirmed the board is actually alive.
Starter prompt:
“SV08 Max, Klipper/Mainsail. Replaced the hotend with an OEM part. Now extra_mcu (CAN toolhead board) won’t connect. Toolhead LED flashes once then goes off. 24V present at the toolhead. The new heater’s pins were wired reversed, and the heater gets hot while Klipper is halted. ST-Link can’t connect to the toolhead MCU. Using Sovol’s SV08MAX GitHub docs, tell me what these symptoms indicate about the toolhead board’s condition before suggesting any fix. Verify wiring claims against the docs.”
Then post the fix when you find it. If people worked the problem and posted the problem AND the solution, this forum would be solved threads instead of filler. AI searches these forums too, so a confirmed fix here means the next person gets a faster, more accurate answer.
Power the printer off until it’s sorted. That heater has nothing controlling it
When installing the replacement hotend, we connected it normally as supplied. We had no warning or reason to expect that the wiring/pin arrangement of a replacement part for the same printer would be reversed or different from the original hotend.
The printer was powered on following the installation, and only after the extra_mcu failure and abnormal heater behaviour occurred did we discover that the replacement hotend’s wiring arrangement differed from the original. By that stage, it was already too late to correct the wiring before the fault occurred.
Had the different/reversed wiring arrangement been clearly identified on the replacement part or in the installation information, we would have checked and corrected it before applying power.
Yeah thank you for the ai advice I appreciate it I think this may be what has caused it. I’ve bought a new PCB and will be wiring it tonight and I’ll then turn the printer on and let you know how I’ve gone
When you say hotend do you mean just the hotend? You will have 2 wires for the heater and two wires for the thermistor. It doesn’t matter which way they sit in the connector. As long as they are in their perspective connector they will both work. The heavy of the two are the hotend heater wires. The thinner almost opaque are the thermistor. The connectors should keep you from mixing them up. However I believe there is an extra port that resembles the thermistor make sure you haven’t plugged into that. Get a pic off the site and confirm you’re in the proper socket.
I personally pulled my entire extruder off and put a reaper on and upgraded to a BTT board. I was tired of all the headaches their boards and firmware gave me. Spent more time throwing unfinished prints away than making things. I’ve completely upgraded my machine and it’s finally a play and go unit that I can count on.
Fancy starting a dedicated thread with the info on those upgrades? It’d be of interest.
yeah i got the chc xl toolhead and the lgx lite extruder looking at building the reaper too.. too many headaches and time wasted
i replaced the pcb board and all was well deleted all demon files went back to srtock files with aux feeder disabled from august then got this error to do with eddy when i went home it wouldnt home properly
it was the pcb on the toolhead its allgood now i replaced it. too many headaches true im looking to upgrade eventually with lgx lite pro and chc xl and a new pcb board
LDC1612 I2C bus busy or timeout error,please check the connection between the sensor module and the mainboard.
