ds-7604ni-k1/4p nvr

I have a DS-7604NI-K1/4P NVR, fitted with a 3TB HDD and 4x 5MP turret camera’s. Over the past few days the 48v external power supply gets very hot until it cuts out completely. It won’t power back up until the PSU has cooled down. When I power it up again with all 4x camera’s connected it will...