UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Closed Thread
 
Thread Tools
Old 3rd Oct 2020, 2:39 pm   #1
Petedox
Pentode
 
Petedox's Avatar
 
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 200
Default 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?
__________________
Pete
BVWS Member
Petedox is offline  
Old 3rd Oct 2020, 3:29 pm   #2
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
Default 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.
G6Tanuki is offline  
Old 3rd Oct 2020, 4:34 pm   #3
Guest
Guest
 
Posts: n/a
Default Re: Transformer help needed!

Quote:
The circuit draws around 75mA.
At what voltage? And why isolated?
 
Old 3rd Oct 2020, 5:13 pm   #4
broadgage
Nonode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
Default 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.
broadgage is offline  
Old 3rd Oct 2020, 5:46 pm   #5
Petedox
Pentode
 
Petedox's Avatar
 
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 200
Default 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!
__________________
Pete
BVWS Member
Petedox is offline  
Old 3rd Oct 2020, 5:55 pm   #6
Orakle42
Pentode
 
Join Date: Nov 2015
Location: Maidstone, Kent, UK.
Posts: 131
Default 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
Orakle42 is offline  
Old 4th Oct 2020, 10:37 pm   #7
bikerhifinut
Octode
 
Join Date: Nov 2013
Location: Penrith, Cumbria, UK
Posts: 1,993
Default 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
bikerhifinut is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 3:41 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.