Hej. I just bought a Beomaster 3000. It looks unused (the owner (in his 70s) said that he bought it 40 years ago and never used it), no scratches, diagram envelope unopened, no dirt on the switches, even the radio preset wheels still have the plastic lid. Everything works as it should, except for the right channel: no sound :( I know there can be many reasons for this. Could anyone tell me where to start my search for the error? The PCB is in tact, no loose connections. When I press "Mono", sound comes out both speakers. Thanks