We have an old house with a neat mechanical doorbell. The bell is one of the hammer/bell kinds. I've installed 2 video doorbells which have been powered by this just fine. I tried to add a 3rd but it adds just too much power draw leading to a constant hum from the transformer and a low level ring from the bell. I read on another forum that adding a 0.5-2 W resistor in parallel with the bell will eliminate this problem without causing damage to the transformer. Would this work? Any alternatives? I'm trying not to have to replace the mechanical doorbell part of the system. It's neat and old and fits the house. Thank you.

  • Just to be clear, this is an electro-mechanical bell, right? Is this an a/c bell? What voltage? 24 V? I can't see how adding a resistor in parallel to the bell would do anything good. The resistor would load the transformer and generate heat (maybe a lot of it). Dec 23, 2017 at 19:34
  • why would you even think that doing something to the bell would resolve a hum that happens when nobody is ringing the bell.
    – jsotola
    Dec 23, 2017 at 21:35
  • Those camera push buttons (at least the Ring, I have installed 2 of them) come with the needed resistor, where is the one that came with your unit? Dec 23, 2017 at 21:59
  • Lighted buttons require a diode be installed across the button. If the problem is the transformer is now too small replace that— same voltage, more VA’s than you have now. Easy fix.
    – Tyson
    Dec 23, 2017 at 22:11
  • The transformer is an ac one, putting out 26 volts with 2 units attached. I haven’t tested it with 3 because it’s a bit tricky to get to the transformer. My understanding of this is that when there is too much current being pulled across the circuit it provides enough power to the bell to make it ring a little. The diode mentioned is for digital chimes and it’s not recommended for mechanical ones because it can damage the transformer (from what I read). The resistor idea came from a posting online but I don’t understand if/why it would work.
    – Elmo
    Dec 25, 2017 at 15:53

1 Answer 1


The resistor across the doorbell drops the voltage across the old mechanical (solenoid) doorbell. If the voltage across the doorbell is too high, the doorbell will buzz. The video doorbells draw a constant current (I measured 132mA on mine).

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