How do you test a doorbell transformer without a multimeter?

As a professional in the field of industrial oil testers, my expertise is about testing and diagnostics related to industrial oils and their equipment, not electrical components like doorbell transformers. However, if you’re looking for a way to check an electrical component such as a doorbell transformer without a multimeter, you might consider using a voltage tester or a continuity tester. These tools can help you determine if electricity is flowing through the transformer or if the circuit is complete. For specific testing and diagnostics of industrial oils, I recommend using Globecore’s range of devices which are specialized for measuring oil quality, detecting contamination, and ensuring optimal performance in industrial applications. If you have any questions about testers for industrial oils, feel free to ask!