Max2Play Home 2016 (en) › Forums › Max2Play on Raspberry PI › Rpi2 + Hifiberry Amp + 7" official Touchscreen = no USB harddisk (no power) › Reply To: Rpi2 + Hifiberry Amp + 7" official Touchscreen = no USB harddisk (no power)
Yes there is 60 watts total in that power supply but it is the amount of current at 5VDC needed to start the display and spin up a hard dive plus power the Pi, the issue of it being the 5VDC that is driving the display and hard drive (not 19VDC) additionally increasing the total inrush current. Even with NO music playing at start up, all the devices draw more current at 5VDC then the Amp+ 5VDC regulator can supply. Lastly during start up at boot or plugging a USB drive in after boot with no music playing, the Amp+ is NOT using 50 watts because No Music Is Playing more importantly the Amp+ is NOT Class A, it is Class D and very efficient so it is never drawing 50 watts continuous. There simply isn’t enough amperage at 5VDC to go around even with the Amp+ drawing minimal current at 19VDC.
One of the solutions to this issue is to add a TSR1-2450 to the 19VDC rail to supply another 5VDC 1A source to power the Display separately. By doing this, there is enough available current for all 5VDC devices.