I started to feel burning smell and... (I would like to repair it)

While I was using my dso Nano v2 I started to feel burning smell coming from it. I don’t understand why I damaged it because I was working with just 12Vpp and it can support 80Vpp.

I opened it and I found L3 burnt.

Looking at the schematic ( <LINK_TEXT text=“https://storage.googleapis.com/google-c … Scheme.pdf”>https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/dsonano/DS0201%20V2.3%20Scheme.pdf</LINK_TEXT> ) I really cannot understand why it happened because USB cable wasn’t connected, and no voltage should have been there in that moment.

Now the battery doesn’t charge no more, and when I attach USB the display backlit goes away. Anyone knows why that ? I understand that battery no more charge, but backlit ?

Anyway now I would like to repair it, but before doing it I would need of some idea about the cause of that, so to avoid that it happens again.

Thank you

The picture of damage:

<LINK_TEXT text=“https://drive.google.com/file/d/1y74U3b … sp=sharing”>https://drive.google.com/file/d/1y74U3bZYStF5fDFPs_fHbuNmfuxNhiEV/view?usp=sharing</LINK_TEXT>