It made sense to get this working first. The ringer circuit goes in parallel with the rest and has a sizeable capacitor to isolate the ringer from DC aspects of the whole phone circuit.
It was fairly easy, but wasn't quite as simple as I had imagined.
I put a 470nF capacitor (rated for 275V) in series with the bell and connected the circuit to the output port on my Sipura ATA. When I rand the ATA I could hear the bell vibrating but no ring.
I set the Sipura ring settings to 90V, 20Hz. That was better, but still not great, and it would only work with the phone in certain positions.
I then discovered that the max voltage from the Sipura is 55V.
But fiddling about with screws on the ringer loosened up the clapper and bingo. I have a working ringer. It makes quite a nice sound, too.
This is not exactly a giant leap for mankind, but it is somewhat satisfying to have an old wooden phone ringing when called.
The next step is to mod the handset by putting in a modern mike and speaker. Unfortunately, I broke the one I was planning to put in, from a spare plain Telecom phone. Slightly annoying, but basic phones cost only $16 in The Warehouse. I got one and will rip it apart for its innards. I will probably use the rest of the innards for this project too.
But first I have to do some day-job work ...
Other related posts:
Old phone plan
Some useful advice about the wooden phone
Old phone has arrived
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