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Old 10th May 2021, 5:08 pm   #1
els1967
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Default Mains transformer wanted

Does anyone have a tran. they could sell me that does 230v to anywhere between 36v to 50v? Two would work ok if they both add up to that range. Can collect if in reasonable range, say about 30 miles. I'm Luton way.

Thanks.
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Old 10th May 2021, 5:09 pm   #2
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Default Re: Mains transformer wanted

Current required?
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Old 10th May 2021, 5:09 pm   #3
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Current?
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Old 10th May 2021, 5:17 pm   #4
els1967
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Default Re: Mains transformer wanted

Ah soz not sure. It's only needed to ring the bells on a few series 300 GPO phones, so not much I would imagine.
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Old 10th May 2021, 8:08 pm   #5
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Default Re: Mains transformer wanted

I thought 'phones used 16Hz for the ring.
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Old 10th May 2021, 8:13 pm   #6
els1967
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Default Re: Mains transformer wanted

50Hz Mains through a tranny is ok if you're not a purist. trying to replicate 16hz starts to get quite complicated. I tried using a couple of relays and a 555 with a d-type flip flop reversing DC between the two relays to the bells. but it didn't really work that well, ok I guess. Works enough for a doorbell. Probably there are better ways to do it.
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Old 11th May 2021, 1:02 am   #7
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Default Re: Mains transformer wanted

Most GPO bells will work at 50Hz but will involve having to sort out the core spacing, this involves a feeler gauge and a spanner, instructions are available online as to how to do it.
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Old 11th May 2021, 2:15 am   #8
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Default Re: Mains transformer wanted

I would use an old audio amplifier and sine wave oscillator.
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Old 11th May 2021, 8:41 am   #9
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Default Re: Mains transformer wanted

I think I may have a Converter Ringing No 7 if that would suit https://www.britishtelephones.com/conring.htm PM if interested.
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Old 11th May 2021, 1:13 pm   #10
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Default Re: Mains transformer wanted

Ringer No 7 now found and done a quick test to confirm operation.
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Old 14th May 2021, 8:07 pm   #11
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Default Re: Mains transformer wanted

Hi Folks, mention of ringing at 16Hz led me to an article in Electronic Engineering for April 1949. This uses ferroresonance principles to generate sub harmonics of the supply frequency,. by using saturating iron cored inductance's .
Illustrated is a ringing generator convertor by the Telephone Manufacturing Co Ltd.
This is also cross referred to in the POEEJ, p110 jan 1944.

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Old 15th May 2021, 1:46 pm   #12
els1967
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All sorted - thread can be closed.
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