I recently purchased and installed a Yale wireless alarm system which worked OK for a few weeks. Then when we came home one day, it showed an error (fault) display that the power supply to the control panel was faulty. I have checked the plug socket, OK, but failed to correct the fault display, now the control panel is completely dead, presumably the backup battery is exhausted. I assume the 12v transformer has failed, so a) how do I replace this without setting off the tamper alarm, and b) will the entire system need reprogramming. Any advice would be appreciated