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Old 13th Jan 2021, 10:52 am   #5
Join Date: Dec 2020
Location: Chelmsford, Essex, UK
Posts: 57
Default Re: Connecting U43 to an Electric Bell

I found a perfect donor telephone for my purposes. A stinky, discoloured cream 706. The smell off this phone actually made me gag once or twice!

I stripped off all of the components and mechanical items one by one until I was assured that I had just enough left to operate the bell. This left the metal chassis, the circuit board, but only to mount the striker mechanism, and the two gongs.
I added a resistor to correct the REN and wired up directly to the U43.

This works perfectly. When I get some more time I will give the bellset its own BT plug and add a nice cover to keep fingers away from the exposed terminals. This is hung high up on a wall so it is safe enough for now.
Everyone in the house loves the sound of the metal bells. Takes me right back to the 70's.

I experimented with the phone by taking out the DIY 205 rectifier. This does allow some unpleasant transients to reach the receiver, so the diodes stay.

Thanks for the tips Dave
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