The PoE blues

Well the long and short of it is that I have a fairly new and fairly expensive PoE surveillance camera and from my own testing I believe that the camera has just shorted itself out internally and taken two PoE power supplies down with it. I’d like to verify this though and I lack the experience or equipment to do so. This is a cry :sob: for help :sos:.

“Well I’d like to help. What help specifically do you need?” you ask. Thank you and excellent question. Here’s some thoughts on that:

  1. Other than this possibly-shorted-out camera, I don’t have any PoE equipment to test my power supplies. Anybody have some PoE stuff I could try the supplies out on to confirm whether they are working or not?
  2. I tried measuring voltages across the pins on the PoE supplies and got nothing. I’m not convinced that means anything because I don’t have the experience to know if there may be an initial autonegotiation going on before voltage is applied. I know there exists PoE testing equipment that would be more conclusive. Anybody have access to any of that?
  3. That camera: I don’t know if there exists some sort of current-limiting PoE power supply that I could try with the camera so I can see if it is actually shorted without blowing another power supply (if indeed they are blown).

Other stuff to know: I opened one of the power supplies and it smelled a bit burnt. So does the camera for that matter. I found a soldered-in fuse inside the power supply and it tests good. I’ve tried multiple cables which I know are good (tested each pin individually with a continuity tester and looked for shorts) so I have ruled out that a cable is the issue. But yeah the plugs on the original cable don’t look too happy. I think they’ve seen a bit of “intense electron action.”


If by “fairly new” you mean “just out of warranty” you have my sympathies. My first suggestion would be to send it in for warranty work. My second suggestion is to assume the camera is bad since it seems to have served two spicy lunches to two PoE switches. Strip the camera naked and look for surface components that look like they got served the same hot meal. Short (ha) of that make a dummy ethernet end where you can supply the camera power then check for thermal hotspots. Anything that hit cables that hard should show something.


The good news is I believe it’s under warranty. I guess you feel my analysis makes enough sense that my guesses of what’s going on are most likely correct. It’s already helpful to have a sounding board — thank you. I’ll start looking into the warranty process.


I know at least with mobile security systems often the suspect part will have burns on the input side from drawing too much current.


Follow that smell with a screwdriver.

Actually since it’s under warranty I’d send it to them angry it blew up the power supplies. Looks like something pulled waaayyy too much current, depending on the power input topology of the camera my guess is a capacitor.

The power supplies themselves may be tricky to fix. I don’t know about ppoe specifically, but power supplies ire pretty easy if you check your line in (spicy wall electrons don’t lick) and follow that path to the output.

There may be a fuse on the output Incase it draws too much current it can protect itself from the load.