[Q] Xperia ZL won't turn on, No LED topic

Hi guys,

I have an Xperia ZL that won't turn on. No response to holding Power button + Vol up or Vol down buttons for 10 seconds. No response to holding little yellow OFF button underneath back cover for 10 seconds .

The phone is connected to known good charger for many hours but nothing happens, no red LED light, no lights at all, no vibration, no screen activity. The phone is not detected when USB plugged to PC running Sony PC-Companion.

Are these symptoms of dead battery? Or when its a bad battery and connected to charger should there be at least red LED or some activity?

Can this be a hardbrick of motherboard? Has anyone fixed their ZL by grounding test point? Do we know what is the correct test point for ZL? I look but can't find in the test point thread: http://forum.xda-developers.com/show....php?t=2646405

Please any ideas to diagnose what is the problem of this Xperia ZL and what to try for fixing? Thanks for any help!