Finished this upgrade Feb-2026. The current firmware (6.4) would not detect the changeover to Core One correctly. In the end to fix this, I flashed (downgraded) MK4S firmware version 6.2.6 which finally detected the Core One changes, and once it switched over, i was able to load the most recent version of Core One firmware (6.4). You may also have to disconnect the door sensor and Buddy Board extension jumper cable to bypass error messages. Hope that helps someone. It cost me hours of trouble shooting.
Prusa, please update this guide to take the built-in belt tuning wizard into account. Right now it asks us to do belt tuning before we even turned the printer on and flashed the firmware. Thanks!
I'm in the same predicament. What did you end up doing? My belts are completely loose, so I'm thinking to tighten them a bit and continue with firmware flashing, and afterwards running the built in wizard. I suppose I will have to skip the self test, as that relies on the belts being correctly tuned(?). Anyway, wish this part of the guide was updated to take into account the belt tuning wizard.
This is quite fiddle. Lots of problems in the comments. Some hints that worked for me: 1) strum it once, not several times, let it read the resonance, not the actual pick. 2) put your finger, lightly, on the belt you are not tuning. I had a hell of a time, until I figured out it was resonating both belts and reading 2 sources. (Also, duh, make sure it's quiet and you aren't reading traffic noise or something.) 3) you probably need several plucks, make sure you get a few readings the same (not necessarily in a row- you'll get exactly what I'm saying when you do it) , and use that as your number. Without any adjustment, I could read 60 to 123, all while it sounded perfectly the same. Don't trust it until you get 3 or 4 the same, that look about right. If you have it tensioned to "that's probably close", don't believe any readings on the upper or lower limits of the app. You're probably within 10-20Hz just by guessing.
My belts are completely loose, so I'm thinking to tighten them a bit and continue with firmware flashing, and afterwards running the built in wizard.
I suppose I will have to skip the self test, as that relies on the belts being correctly tuned(?). Anyway, wish this part of the guide was updated to take into account the belt tuning wizard.
1) strum it once, not several times, let it read the resonance, not the actual pick.
2) put your finger, lightly, on the belt you are not tuning. I had a hell of a time, until I figured out it was resonating both belts and reading 2 sources. (Also, duh, make sure it's quiet and you aren't reading traffic noise or something.)
3) you probably need several plucks, make sure you get a few readings the same (not necessarily in a row- you'll get exactly what I'm saying when you do it) , and use that as your number. Without any adjustment, I could read 60 to 123, all while it sounded perfectly the same. Don't trust it until you get 3 or 4 the same, that look about right. If you have it tensioned to "that's probably close", don't believe any readings on the upper or lower limits of the app. You're probably within 10-20Hz just by guessing.