If your doorbell is malfunctioning, see if the transformer is still working. These can wear out over time. They're not that difficult to remove and replace.
Things You'll Need
Turn off the main switch of the circuit that supplies power to your transformer. Check it with a voltage tester to make sure it's off.
Open your doorbell's junction box, where you'll find the transformer attached to your doorbell beam.
Locate the AC wires on your transformer that are connected to a few wire nuts or screws. Remove the electrical tape in case one is attached to the wires. This reveals the two splices that are attached to your transformer.
Go to the other side of your doorbell transformer and locate the two nuts or screw terminals. These are connected directly to your door chime and button from your doorbell transformer. For each terminal, you should see one wire. Label each wire by marking them with your masking tape and marker to remember where they were plugged.
Remove the nuts or screws. Unplug the wires carefully.
Pry off the doorbell transformer completely with a screwdriver from its mounting hardware.