Ok thank you I get you now. I have a big collection of bezels that of got over the years but they are all curved. Where would I get some basic non curved ones. Thanks

Thanks Mitu!! It seems that adding/enabling these lines in the config.txt fixes the problem sdtv_mode=2 #My tv is PAL sdtv_aspect=1 #4:3 audio_pwm_mode=0 dtparam=audio=on (this one is enabled by default)

Oh! I never thought that this can be the solution. With another USB-Cable there is absolutly no problem. Thank you very much!