Amplifier barely produces bass signals after a lightning

[aca94sss]

Hey guys! People who understand electronics should try to answer this, thanks. I've got 5.1 system hooked to a pc with AUX, Microlab A-6662.
After a lightning that struck close to my house, I've noticed that my amplifier barely giving bass signals to a subwoofer (subwoofer itself is totally ok).

Main question important for me is: What part inside of the amplifier that is making bass could be malfunctioning? So I could look for it with the instrument. Thank you !

 

[americanaudiophile]

There should be an amp just for the subwoofer. Trace the wire from the subwoofer speaker to it. It might be a chip amp.