The blue light comes on when the power is turned on. I've tried connecting various things and fiddling with the knobs, but there's no sound. To be honest, I don't understand it very well. I haven't taken it apart. Looking through the ventilation gaps, the circuit board is very clean and there's almost no dust. The condition and exterior are generally clean. However, because of my careless storage, there are a few scratches on the top. I probably think it's broken. It's being sold as junk. There is no warranty. For those who can fix it, or for parts. I think those who are not familiar with this should not buy it, thinking they can use it. I've looked up various things on my smartphone and tried connecting it and adjusting the knobs, but no sound came out. I think someone who is familiar with amplifiers or has a hobby in this area could easily fix it. Everything in the photos is included.