I have been working on an intercom system installation and once installed have found that the transformer / control point has a 18.5v DC output when it is supposed to have an output of 8v - 9v DC. I have since discussed this with the supply company and they have sent a replacement which is the same. The supplied door locks / entry systems are rated at 8 - 12v and they keep burning out. Can anyone recommend anything to reduce the supply voltage. I have considered resistors but the current is unknown at this point and am concerned they could burn out. Any ideas welcome thanks.

 

Your going to need to supply a schematic of the power supply, if you want people to help.

Is this just a walwart supply? If that is so then that is your answer.