Dual rail supply, no centre tap - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th July 2006, 12:39 PM   #1
diyAudio Member
 
Join Date: Jul 2006
Question Dual rail supply, no centre tap

I am building an amp kit with a dual rail supply. The transformer i have has no centre tap. Is it possible to use this transformer or do i have to get another one? It has dual secondaries.
  Reply With Quote
Old 13th July 2006, 12:57 PM   #2
diyAudio Member
 
Holger Barske's Avatar
 
Join Date: Jan 2001
Location: Ruhrgebiet
If it has dual secondaries, just tie one secondary's "start" and the other's "end" together, and you have a center tap.
__________________
Best regards: Holger
www.holgerbarske.com - Deutschsprachiges Paradise-Support-Forum
  Reply With Quote
Old 13th July 2006, 12:57 PM   #3
Wynand is offline Wynand  South Africa
diyAudio Member
 
Wynand's Avatar
 
Join Date: Mar 2005
Location: Cape Town
Take the two secondaries and connect the "neutral" of one secondary and the "live" of the other secondary and tada...
A centre tapped trannie.

If I've offended anyone with the terminolagy please let me know how to phrase it.

---- || ----- +
) || (
) || ( Secondary A
) || (
) || ------ -
) || ------ +
) ||(
) ||( Secondary B
) ||(
---- || ------ -

In other words. Connect the - of Secondary A and the + of secondary B.

To check If you've got the phase correct. Put a VOM accros the + of Sec. A and the - of Sec B. If it reads +- 0V then one of the secondaries is the wrong way round. If it reads the sum of both secondaries, it's right.

There is some other threads dealing with this. Look at them too.
  Reply With Quote
Old 13th July 2006, 12:59 PM   #4
Wynand is offline Wynand  South Africa
diyAudio Member
 
Wynand's Avatar
 
Join Date: Mar 2005
Location: Cape Town
My Ascii art sucks. Hope you get the picture though.
  Reply With Quote
Old 13th July 2006, 01:00 PM   #5
Wynand is offline Wynand  South Africa
diyAudio Member
 
Wynand's Avatar
 
Join Date: Mar 2005
Location: Cape Town
A mere seconds too late on my first post.
  Reply With Quote
Old 14th July 2006, 02:42 AM   #6
diyAudio Member
 
Join Date: Dec 2005
Location: Atlanta
Default Re: Dual rail supply, no centre tap

Quote:
Originally posted by leonrocks
I am building an amp kit with a dual rail supply. The transformer i have has no centre tap. Is it possible to use this transformer or do i have to get another one? It has dual secondaries.
Another obvious answer is to get a transformer with a center tap. It may be easier.
  Reply With Quote
Old 14th July 2006, 04:02 AM   #7
diyAudio Member
 
Join Date: Sep 2002
Location: Sweden
Default Re: Re: Dual rail supply, no centre tap

Quote:
Originally posted by ezkcdude


Another obvious answer is to get a transformer with a center tap. It may be easier.
Why? Such a transformer has two secondaries two. It is just that they have tied two ends together, so you don't see it. It is better to have access to both secondaries, since it gives more flexibility. It makes it possible to use a better grounding scheme, for instance.

Of course, if using it as a center tap one, it is important to tie the right two ends together, but as long as they belong to two different secondaries, the worst that can happen is that the two secondaries cancel so you get zero volts in total.
  Reply With Quote
Old 14th July 2006, 11:28 AM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi Christer,
Quote:
the worst that can happen is that the two secondaries cancel so you get zero volts in total
this made me draw a diagram to check what you said. Yes, you're right , that is the worst that can happen.
That diagram saved me from an embarassing ......

A completely different case from connecting the primaries out of phase.

Ez,
go and do some more homework.
Quote:
Another obvious answer is to get a transformer with a center tap
NO!!!
__________________
regards Andrew T.
  Reply With Quote
Old 14th July 2006, 01:40 PM   #9
diyAudio Member
 
Join Date: Dec 2005
Location: Atlanta
Quote:
Originally posted by AndrewT
A completely different case from connecting the primaries out of phase.

Ez,
go and do some more homework. NO!!! [/B]

You got me. Now you see why I didn't want to use a transformer for my own PSU project. Anyway, I did find a link which is helpful (to me, at least) from Hammond:

http://www.hammondmfg.com/5CHook.htm
  Reply With Quote
Old 14th July 2006, 01:59 PM   #10
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi Ez,
Hammond is a nice link. Unfortunately the Hammond page does not alert the user to the possibility of incorrect wiring consequences.

The first diagram showing the series primary connections shows the correct way to wire them for, usually, 240Vac supply.

If 2 to 4 or 1 to 3 were connected instead of 2 to 3 or 1 to 4 then the transformer goes into almost instantaneous destruction mode.

Note, there are four ways to do the primary series connection and a 50% chance of blowing the transformer. The plug top fuse (UK) and/or the distribution board fuse should prevent more serious house damage.

Since finding the light bulb trick, here on the Forum, I never fail to use it for all my maintenance switch on. It will save the transformer from all miswiring errors and may save the downstream semiconductors from terminal damage as well.
__________________
regards Andrew T.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Using split rail supply for single rail DC DanX Chip Amps 1 15th March 2008 05:18 PM
Dual regulators for single rail? leadbelly Power Supplies 7 10th February 2008 09:28 PM
transformer question (dual secs same as centre tap) homertooties Power Supplies 0 11th June 2007 08:12 PM
Building a dual rail battery power supply? pjpoes Parts 4 22nd January 2007 08:10 PM
Dual Rail JLH ('69 variant) Mike L. Solid State 0 26th March 2006 04:08 PM


New To Site? Need Help?

All times are GMT. The time now is 11:10 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2