If no sound is produced or there is no sign of life check the LED signs of the Logic Board. From there you should be able to check the light indicators on the logic board itself and see what exactly is going on. If the first LED is lit up then that means that the computer is receiving power but is not processing it properly and is either a bad power supply ( knowing that you replaced it recently it could still be bad, just maybe a faulty one was sent to you, rare but it does happen unfortunately) or a bad Logic board itself. IF you have any other questions just ask!