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I have a Ring video doorbell that is connected and functioning to the old doorbell wires, which I measured at 16V.

I also have a old Nutone Scoville 10 V, 5 VA transformer tucked in a very hard to reach space in a stairwell (see picture). This transformer creates a very annoying buzz constantly, and I'd like to pull it. I believe that it is somehow stepping down the voltage to 5 V to work with the doorbell chime.

However, I was unable to get a suitable reading on the chime. When at rest, it measures 0.20 V and then drops to about 1 mV when the doorbell is rung.

My theory is that I could simply buy a new 16V doorbell, throw away this transformer and connect the two red wires in the picture to each other. Since the Ring is at 16 V, that tells me there is another transformer hidden under the floor that I don't hear and can't see.

enter image description here

But I'm not sure exactly how these old transformers worked and can't find any instructions online. Thank you for your help.

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  • \$\begingroup\$ That is a transformer. The output voltage is 10V AC. It provides 5VA of power. If you measure the output with a DC voltmeter then you will get incorrect results. \$\endgroup\$ – JRE May 7 at 15:49
  • \$\begingroup\$ Yep - I measured with AC which is how I was able to measure the wires feeding the doorbell at 16V. I want to know what this transformer is transforming - is it stepping down from 16V to 10V? I can't measure easily from the transformer itself - it is in a very tight space that I could just barely squeeze my phone into to take the picture. I cannot find any old wiring diagrams online. \$\endgroup\$ – David Gallagher May 7 at 16:24
  • \$\begingroup\$ It is more likely transforming 110VAC down to 10VAC. \$\endgroup\$ – JRE May 7 at 16:25
  • \$\begingroup\$ That's what I'm thinking. I'm thinking this is actually the only transformer, and the Ring is able to draw almost 16V from it (based on other posts online), even though this is a 10V transformer. (apparently their voltage load is quite variable/volatile). If I just replace this transformer, I should be good to go. Hopefully. \$\endgroup\$ – David Gallagher May 7 at 16:42
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    \$\begingroup\$ I’m voting to close this question because it should be migrated to DIY.SE \$\endgroup\$ – Elliot Alderson May 7 at 17:33

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