No POE power from port on POE NVR

[Revo2Maxx]

So today a friend of mine asked if I would come look at his Hikvision 2020 16ch POE NVR, I told him I may not know enough about the device but I would be happy to look it over and see what I can find. So I will admit I took some steps I might not have needed to take, I just did it to make sure I was getting full power to the POE part of the NVR. To start with, I marked all the cables so they would go back to the right ports, I then removed the top, and disconnected the 2 drives from the PCB. This way I was sure if it was a voltage issue or current issue from the Power supply that it might have helped. Plugged in a camera and still no power, I then tested the power supply input to the PCB and it had 52+ volts from testing at 1 yellow and one white wire. I then did a good look over the top of the PCB and there wasn't anything that said it should have been dead from the top. So I removed the screws from the PCB holding to case and all the wires so I could pull it from case. I then tested the Very large Protection diode and sure enough it was shorted. I removed it from the PCB and (don't use it like this for long) however I didn't have a new diode on me that size so I put the PCB back in the case, connected it all and turned on the power supply and waited for the NVR to load, Once it was loaded, I then added one of his cameras and sure enough it powered on. So I then tested a few other ports to make sure they were all working testing 1,4,6,9,13 and 16 and they all powered up. So I did tell him that I wouldn't run the NVR without the Protection diode for long and if there was some cameras that he could omit until he could get a new Diode installed i would run it with only a few cameras that were most needed.. (I mean it blew once already for some reason) now without a protection diode something worse might blow..

Anyway I thought if you had a POE NVR that isn't powering your Cameras and you know the power supply is good. Look for the POE protection diode as somewhere to start looking. On this 2020 NVR the protection diode was on the bottom of the PCB next to some large caps. Testing it, it was shorted in both directions. Again don't remove it and for ever run it without buying a good replacement for use as next time it might damage something worse.