On 08/11/16 15:34, WeeBob wrote:
Hello.

I have an old wired doorbell that has an 18V DC power supply. The
actually transformer has been (I think) channelled into the wall, or
underfloor boards in the attic. i.e. hard to get to.

A new fancy doorbell requires connection to a 8V AC power supply.

Is there a simple way to do this? i.e. 18V DV in, 8V AC out?

Thanks.

You will probably find that the new bell only requires 8V AC because it
converts it internally to whatever DC voltage it requires to operate,
possibly by no more than a rectifier and smoothing circuit. You could
try connecting a 7.5V DC supply to it to see if it works (and change the
polarity if it doesn't). If it does, and you want to be bothered, you
could try one of these:
http://www.ebay.co.uk/itm/DC-4V-38V-...-/122202388683

And select the voltage output which you have checked works ok. Whatever
you do, don't connect up the 18V DC supply directly to the new bell.

--

Jeff