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 16th Mar 2018, 7:39 pm   #1
eddie_ce
Hexode
 
eddie_ce's Avatar
 
Join Date: Aug 2010
Location: nr. Hannover, Germany
Posts: 372
Default Output transformer question

Hi,

one of my current projects is building the signal tracer Smithy presented in the March 1970 edition of the much missed Radio Constructor. The output valve is a 6BW6 and an OPT of 45:1 for 3 Ohm LS was specified.

As the output stage will normally not be running at any significant power and will have a low duty cycle, I am thinking of using a 100V PA system transformer with a primary impedance of ~ 4600 ohms into a 4 ohm LS.

Will this be OK or are there any pitfalls to watch out for?

As always many thanks for taking the time to read and reply..
__________________
Eddie
BVWS Member.
Friend of the BVWTM
eddie_ce is offline  
Old 16th Mar 2018, 7:51 pm   #2
Trevor
Octode
 
Join Date: Aug 2006
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 1,082
Default Re: Output transformer question

Core saturation the 100 volt line unit has interleaved E and I so it's likely to suffer from core saturation. Having said that I have used them with a fair result. You could always pull the laminations and then rebuild. I have also done this, but I did not think it was worth the effort.

Trev
Trevor is offline  
Old 17th Mar 2018, 12:06 am   #3
joebog1
Banned
 
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
Default Re: Output transformer question

AS you state: the duty cycle is very low, you dont need hi-fi response, and you won't be using full power, so "any" small single ended transformer should work. If you do have real problems ( you shouldn't ) then I am sure somebody here can find such a transformer.

I have seen many projects using line transformers as output stages, so maybe a look at some of the guitar amp builder's sites would give you more accurate advice.

Best of luck
Joe
joebog1 is offline  
Old 17th Mar 2018, 10:05 am   #4
Cobaltblue
Moderator
 
Cobaltblue's Avatar
 
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,823
Default Re: Output transformer question

As Quality isn't that important you could try a 6V mains transformer.

It will saturate and the HF response won't be that good but such transformers are cheap and plentiful might be worth an experiment to see if it's good enough in this use

Cheers

Mike T
__________________
Invisible airwaves crackle with life or at least they used to
Mike T BVWS member.
www.cossor.co.uk
Cobaltblue is online now  
Old 21st Mar 2018, 4:01 pm   #5
peter_sol
Octode
 
Join Date: Aug 2003
Location: Welwyn Garden City, Herts. UK.
Posts: 1,906
Default Re: Output transformer question

A 100v line transformer will be too low an impedance.
peter_sol is offline  
Old 21st Mar 2018, 9:36 pm   #6
Trevor
Octode
 
Join Date: Aug 2006
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 1,082
Default Re: Output transformer question

Not quite true some 100 volt line units can be anything from 10 k down to 1k the main problem with them is core saturation
ren
Trevor is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 12:07 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.