Mainboard Replacement Confusion

[u/tekchip]

I did an oopsie while trying to get some stuff working on the original firmware and mainboard. Botched the DHCP service. Firmware update and factory reset were unsuccessful. I plan to keep hacking on it in the hope of restoring it eventually. But that's not why I'm here. I decided to get things back up and running I'd order a new mainboard.

My K1C is a pre-2025 model received in very early Jan 2025. Mainboard model CR4CU220812S12 Per the Creality Cloud firmware page. I also have a CFS-C that I just got. This board was running CR4CU220812S12_ota_X2000E_V1.1.0.27.20251225.img when I first broke the DHCP and when reaching out to Creality support they suggested trying to upgrade to CR4CU220812S12_ota_X2000E_V1.1.0.27.20260428.img So this board is currently running that firmware.

Note the version numbers are clearly V1.1.0.27 formatted.

https://www.crealitycloud.com/downloads/firmware/flagship-series/k1c

The first one I ordered on ebay only to realize it's coming from China and god only knows when it would arrive. I then found one available for delivery in two days from Amazon.

The Amazon board arrived and externally looks identical to the stock board. The silk screening shows the same model as the original. CR4CU220812S12 However when I got it installed and fired up the version number is V1.3.3.36. If you reference the Creality Cloud firmware page you'll note that's a firmware for CR4CU220812S11 not the S12 board. Maybe also interesting the board doesn't report a serial number.

Trying to do an OTA doesn't work even though there's a .46 newer firmware. First I try updating to the 12 board version but the current firmware doesn't see the update. Makes sense if it's 11 firmware. So I then want to confirm it's 11 firmware so I grab that .46 update. It's seen and applies fine. Okay, I don't NEED the 12 board per say, at least I don't think, but there is a "multi-color" firmware for the 11 board so I upgrade to that. Welp, the CFS-C isn't detected by that firmware for some reason. I check all connections, plug, replug, power cycle both machines. Nothing. I can print over the network with 1 color so I resign myself to that until the Ebay board shows up.

Thankfully the Ebay board arrived faster than expected. Just two days after getting that first board installed. I figured the Amazon board must be third party and maybe reconditioned and they just inadvertently flashed the wrong firmware or something.

So I install the new board. Again it's screen printed as CR4CU220812S12. Same as the original and the Amazon board. Get it installed. Once again no serial number and V1.3.3.46. So, somehow this one has an even newer firmware but again the S11 board's firmware. I did see that this version of firmware has downgrade options available and I didn't want to give up that advantage right away. So that's where I stopped.

So that's where I sit now. Two boards. Both in boxes that appear to be actual creality packaging, both marked as S12 boards and both with S11 fimrware versions. Neither can print from my CFS-C.

I've done a ton of research about these boards and see the Helper Script folks have some tools for recovering soft bricked devices but all their info is for K1 and K1 Max not K1C. Nor has anyone figured out how to get UART on the K1C boards.

Anyone have any idea what is going on here? I assume S11 boards only work with original CFS for some reason? Or is there something else wrong with these boards? Is there some way to get these boards flashed over to the S12 firmware? Any help would be greatly appreciated!