Works on power but won't turn on when on battery (new battery)

Hi all,

I have a Harman Kardon Onyx Studio 1 (never opened up) that I realised would not turn on unless the pwer was plugged in. I’ve had this unit from new so just figured it was a dead battery.

I ordered a new one and installed it but I’m still facing the same problem with the newly installed battery. It shows as charging when plugged in but when I unplug and try turn it on it beeps and then immediatley dies.

Would anyone have any idea as to why it would’nt be working, I’ve had a look and cant see anything obvious.

Thanks, Andy.