Hacking Question Switch Doesn't boot into OFW

[Matenka]

Hi All.

My Switch was running OFW Firmware 9.0.0 CFW: Atmosphere 0.9.4
Rolledback to an known working 8.1.0 Nand Back UP and then the switch could not boot into OFW anymore.
Checked with BRiccmii > 11 Fuses burnt, even tough 9.0.0 was installed with ChoiDujourNX to prevent exactly that.
After Reroll can't get into OFW even with Hekate > just black. [Auto RCM OFF]

What i've been trying:

• Tried booting into Amtosphere > Black Screen after Sept logo.
• Rolledback Nand Back-UP via Hekate > Reboot OFW > X
• Rolledback Nand Back-UP via Hekate > Reboot OFW > Hold Power + Volume up + Volume down > X
• Rolledback Older Nand Back-UP via Hekate > Reboot OFW > X
• Rolledback Older Nand Back-UP via Hekate > Reboot OFW > Hold Power + Volume up + Volume down > X
• Formated SD Card to FAT32 Instead of EXFAT, retored Boot0 + Boot1> X

Messed up by:

• Not making Nand Back-Up before rollback
• Not making Boot0 + Boot1 Back-Up before rollback

Could it be:

• Boot0 Corrupted?
• Boot1 Corrupted?
• Nand Back Up's Coruppted?!?
• To do with not wiping Save Data?

I'm starting to get to my wits end here. I know i can salvage this, but honestly have no clue anymore.
Gonna try the wiping the save data i've been reading about, but if any of you have an idea im open for any suggestions.

 

[Lacius]

If you ever booted your Switch normally (i.e. without a custom bootloader like fusee-primary or Hekate), probably without AutoRCM installed, then you burnt your fuses. It is now impossible for you to boot your system normally without a custom bootloader, unless you upgrade back to 9.0.0 or higher.

Did you restore your 8.1.0 BOOT0/1 backups when you restored your 8.1.0 NAND?

Is your SD card exFAT or FAT32? It needs to be FAT32 if you don't have the exFAT support update installed.

 

[Matenka]

I did restore the Boot0 and Boot1 from 8.1.0. with every Nand backup attempt I tried.

Got one SD card on exfat [main] and one on fat32 [right now at least]. The exfat update was installed. And 9.0.0 was installed with the exfat option in ChoDujourNX

 

[Lacius]

I did restore the Boot0 and Boot1 from 8.1.0. with every Nand backup attempt I tried.

Got one SD card on exfat [main] and one on fat32 [right now at least]. The exfat update was updated. And 9.0.0 was installed with the exfat option in ChoDujourNX

I recommend following this guide:
https://switch.homebrew.guide/usingcfw/manualchoiupgrade

This guide will allow you to do a clean install of 6.1.0 or lower. Your fuses will still be high, so the system will only boot with a bootloader like fusee-primary or Hekate, but it should get you up and running again.

 

[Matenka]

Thanks I'll look into it tomorrow. Will post my results.

Edit: Who needs Sleep!

Thanks @Lacius you were right on the ticket.
Had to completely i had to wipe all my Save Data etc from the system with memloader.
But that's fine. Had most of it backed up regardless.
Thank you very much sir.