I have uploaded 3 versions of the X5105 factory instruction manuals - of different ages.
They are in their own directory inside the group "Files" directory or section.
Hopefully there will be the correct firmware update instructions for your radio in one of these versions of the manual.
You could also try this web site page at Radioddity, the dealer where I got my X5105.
https://www.radioddity.com/blogs/all/how-to-update-xiegu-x5105-firmware-2021-latest-guidance
Good luck!
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Doug, K8RFT
