Bose Companion 3 Series 2 no power at all

I have not used the speaker for a long time, and then when I used it for a month, the speaker just stopped working, and no power at all. I have a little bit of knowledge in Electronics. I have successfully removed the rear module assembly and checked the unit for any abnormal things that I could see on the PCB, and tried to magnify the PCB for any defects on the components, and cleaned the PCB with an alcohol cleaner. The only problem is that I need a schematic diagram, and I need advice and help if you have an idea to rectify the problem. Thank you so much for your help.