kregg451

I recently added 4 Zmodo cameras to a 16 channel DVR with 8 existing cameras. Two of the added cameras are showing nothing but black on the monitor. The DVR is not showing video loss and it doesn't matter which port they are plugged in to. If power is disconnected and then reconnected the picture comes back and then gradually fades to black in a few minutes. I'm not sure if it's a power supply issue or a wiring issue. Any ideas?