which parts I have to change?

@killergitarre what was wrong with it before you took it apart? What did not work? What did you check?

After providing mains support i switched the B212D on, but the only thing that happend was, the power LED flickered after a few seconds for about 1 second, but the device did not power on. I opened the Speaker according to the guide, the main fuse was ok and the P0A2E-Board seemed to work properly. So i went on disassembling the device to the Amplifier Board but could not identify any of the "bulked" capacitors.

So i would be happy for any further help.