During the course of my recent cleanup I came across 6 fairly expensive dome cameras that were replaced (faulty) last year from a pub. These & the DVR suffered from a power surge during a lightning strike. I kept them with the intention of doing a post mortum & finaly got the chance today. They were dual voltage 12vdc/24vac cameras. Turns out that every one of them suffered damage to the rectifier/regulator board which is seperate from the camera electronics. Remove the faulty board , rewire the power input & they ALL worked perfectly on 12V.
Just something to consider if you have dual voltage cameras that have given up