Hello I have an old DGX620 keyboard and last week I conected some usb line cable and instaled the usb/midi drivers in my computer, so I put my DGX on PC mode, my computer recognice it, everithing ok I play it in Ableton, it sounds great, but next day I turn on the keyboard and instantly the computer recognice my keyboard with out being in PC mode so is strange cause there are 2 diferent sounds at the same time, one from the keyboard speakers and other from the PC speakers, it sounds very cool and I play a lot like 4 hrs making new sounds, the problem is next day my DGX cant turn on, strange I suppose is the power adapter and i was correct it was damaged, so I fix it, but still my keyboard doesnt work, I take my keyboard to profesional support and they fix it for me, but they tell me that the internal amplifier was blown up, locally the computer of the keyboard dosesnt suffer any damage, they said me the cause was probably to much voltage from my house, i explained to them the usb line cable thing but they said it didt matter cause the usb voltage was independient from my power adapter. any theory or explanation?
I know the usb/midi cable can suply 5V to my keyboard and my power adapter is giving me 15-16v (wich is moreless ok, a little high but 12v cant power my keyboard)
I cant find any similar problem like mine, contrary I read post of people that can play perfectly with out put pcmode and have the two output sounds at the same time, whats going on? i dont want to conect again my Keyboard to the computer, I know that the problem is electric but dont know exactly why can some one explain please?

So In resume

DGX620 + USBcable + No PCmode = Burned Power Adapter + Burned Internal Amplifier.

Cheers