Accidentally connected about 11 volts

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@incp|new_window=true] where and how did you apply that voltage? I expect the battery and the power management IC to have gone up in smoke. Possibly more components. Time to open it up and tear it down to see what got damaged. Sony Ericsson W580i Repair Once you are at the motherboard check around the charging port and inspect all the components. For anything odd etc., post some pictures of it with your Question. that way we can see what you see. Adding images to an existing question

I don't know where and you did apply that high voltage. I except that the charging port and power management IC have been gone in smoke. If you haven't opened your Walkman after the voltage damaged it, possible more components (like internal flexible cable, display, LCD flexible cable, front keypad UI and keyboard UI) have been destroyed. Phones don't have a fuse if it is dead.