I received a call from a customer to say their CCTV system had stopped working, on a very stormy night with strong winds and heavy rainfall, and could I fix it? The problem is now solved but I thought I'd pose the scenario here as a bit of fun to see what others think might have happened. I'll post the solution in a couple of days.
The customer has an 8-channel Dahua HD-CVI DVR connected to 8x HD-CVI 1080p cameras. The power to the DVR, to the attached Samsung monitor and to the 8 cameras is protected by a UPS which provides 20+ minutes of battery power. An ethernet cable connects from the DVR to an ADSL router/modem which is not protected by the UPS.
The customer reported that his monitor was black and he couldn't see any camera feeds on screen. I attempted to remotely access the DVR and found I was able to connect but all the cameras showed black. This meant the DVR was still alive which was good news. I found the DVR was recording black video. Next I went back to the last occasion on which the DVR had recordings from the cameras. Every camera showed similar symptoms. Here is the view from camera 8.
The first second or two show the normal night time IR image. Then the picture starts to break up. What struck me as particularly odd is that parts of the corrupted image cycled through scenes from several of the other cameras, and not just from camera 8. How and why would that happen, I wondered? After a few seconds, the image went black and stayed that way. The same symptoms could be seen on all 8 cameras.
Question: What was the cause of the black video problem and what is the solution? Sorry I don't have any IPVM lanyards to give away as prizes!
I'll post the solution in a couple of days but know there are some members who love troubleshooting and might have a little fun working out the problem and solution. Feel free to ask questions if more information is required.