Jollyrgr

Could be drunk, could be incompetent, could be a mistake. At work professional union electricians wired 120VAC outlets for 208VAC. Luckily this was in the PC Techs area and the first thing they plugged in was a set of speakers. The tech was smart enough to know something was not right as the speakers were buzzing. She told the electrician something was wrong and he measured the voltage at 208VAC. But if you read the original post again it states that a SECURITY CAMERA INSTALLER was installing these cameras; not an electrician. The poster is asking for help from electricians (I'm assuming they wanted Electronic Technician but did not specify that.)

I work heavily with the security department at work. They have both 12VDC and 24VDC cameras. There have been "OOPS" where a 12V camera has been hooked up to 24VDC and that spells doom to the camera. But I've also seen the electrician that hooks up the 12VDC cameras use 16VDC supplies. The cameras do not instantly fry or anything like that and continue to run just fine. What DOES damage cameras is reverse voltages. In these devices, and other things such as CB radios, you will find a reverse polarity diode strapped right across the DC input. The idea being that if you connect up a reverse polarity supply the diode will conduct heavily and blow the fuse. Sometimes, especially when no fuse is used, the diode will short out. This results in blowing of fuses, or in the case of no fuse, sparking when power is connected. I believe you have one of three things going on. 1) You are hooking the power supply up backwards. (You have confirmed with a meter that you have a 12VDC power supply and NOT a 12VAC power supply, right? You've also confirmed WITH A METER the polarity of the two wires.) 2) The protection diode has shorted. (With a Ohm meter, check the resistance reading in BOTH directions on the DC input of the camera. You should get two different readings depending on which way you connect the probes. If you get a VERY LOW reading, similar to when you touch the leads together, then you possibly have a shorted protection diode.) To replace a shorted diode is, if you know how to solder on a PC board, extremely simple. Normally these diodes are right at the power input to the device. 3) The worst case; there is something damaged in the camera. This being the case it will become very difficult to troubleshoot remotely. As others have said the cameras usually take in a range of voltages and regulate the power down to another voltage such as 5VDC or 9VDC. I hope this helps.