Hooked up an new transformer and it tested fine at about 15v. When I hook up the doorbell wires to it, the power stops completely (no reading of power). When I unhook the doorbell wires, power comes back at a perfect 15v. Could this be caused by a faulty chime or actual doorbell buttons being bad? Something had to have caused the system to stop working in the first place, I just assumed it was a bad transformer. Sometimes I wish I was an electrician and understood this seemingly simple stuff better.