Hard brick or what else ? topic

I own a old Nexus S. I think its soft bricked. One time, the phone fall and the battery goes out. I put the battery on the phone, and the phone does now what do you see on the picture. When i put the battery, the screen makes light, but nothing more. The battery doesnt charge anymore, and i tested the battery with a VoltMeter :4V. I tested the battery mainboard connector, and i have.... 0V, when connected to charger or USB port of my laptop !

I tried VOL+ and Power, then pluging the battery holding Vol+ and power, and still the same blank screen. Means bootloader is corrupted ?

Thanks for answers !

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