Hi,
I have the exact same issue with a recently purchased WiiU.
- Blue light, black screen, no image in recovery menu.
- Managed to blindly access minute and it is showing the menu.
- made a backup: otp.bin, seeprom.bin, seeprom_decrypted.bin, BOOT1_SLC.RAW, BOOT1_SLCCMPT.RAW, SLCCMPT.RAW...