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3rd Oct 2020, 2:39 pm | #1 |
Pentode
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 200
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Transformer help needed!
I've built a multiplex decoder which I need to power from an isolated source inside a valve FM tuner.
I'm using 6.3v from the end of the heater chain. The circuit draws around 75mA. Can someone tell me where I can obtain a small cheap 1:1 transformer that will do the trick?
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Pete BVWS Member |
3rd Oct 2020, 3:29 pm | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
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Re: Transformer help needed!
Could you perhaps use a transformer that has two independent, equal-voltage secondaries? Since you'd not be using the primary the pri:sec turns-ratio isn't of concern here.
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3rd Oct 2020, 4:34 pm | #3 | |
Guest
Posts: n/a
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Re: Transformer help needed!
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3rd Oct 2020, 5:13 pm | #4 |
Nonode
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
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Re: Transformer help needed!
Agree, you need a transformer with two independent 6.3 volt windings.
Use one as the input from the existing heater circuit, and the other as the input to the extra circuitry. This arrangement tends to produce a little less than 6.3 volts, but should be acceptable. Ignore the mains voltage winding. Make certain that the existing heater supply can handle the extra load. Alternatively, it might be simpler to fit an additional mains transformer with a standard mains voltage input and a 6.3 volt output. |
3rd Oct 2020, 5:46 pm | #5 |
Pentode
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 200
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Re: Transformer help needed!
Thanks G6Tanuki, I've just found an old PCB mounting transformer with 6-0-6 secondaries, (both rated at 300mA), and it works fine.
Broadgage, as you say, there is a slight loss (to 5.9v) but that's no problem at all. It was a relatively simple solution that hadn't occurred to me - thanks for your help!
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Pete BVWS Member |
3rd Oct 2020, 5:55 pm | #6 |
Pentode
Join Date: Nov 2015
Location: Maidstone, Kent, UK.
Posts: 131
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Re: Transformer help needed!
I would agree with broadgage, assuming the decoder is a semiconductor device,
a small 1.5VA mains transformer would be a simple solution if an isolated supply is required. It also removes the possibility of overloading the existing heater supply. Orakle42 |
4th Oct 2020, 10:37 pm | #7 |
Octode
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
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Re: Transformer help needed!
seconded, why make a simple job complicated. if you're going to use a transformer anyway, cut out the middle man and get one of he many sub min jobs out there
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