Need help with dual secondaries in series - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 10th November 2007, 07:38 PM   #1
glt is offline glt  United States
diyAudio Member
 
Join Date: Oct 2004
Default Need help with dual secondaries in series

Hi, first pot here. I'm building the chipamp.com PS and used a transformer with dual 30V secondaries. However, the secondaries are in series (only 3 leads.It is not center tapped as the voltage across both secondaries is 60V). As you may know, I get separate virtual grounds in the chimpamp.com PS. I am able to get +40 and -40 v. However there is 30V between the two virtual grounds of the PS, so when I shorted them (thinking they could be shorted) I burned a bunch of fuses.

After thinking about it, it kind of make sense since the virtual ground of the secondaries (the zero volt of the sine wave) must be some volts apart since the secondaries are in series.

So the question is: is there any way I can get the grounds of PS at the same level (since I need to connect them to the ground of the amplifier. (I am using the Hypex UCD180)

Thanks in advance for any help.
  Reply With Quote
Old 11th November 2007, 11:04 AM   #2
diyAudio Member
 
Join Date: Mar 2004
Location: Arkansas
Hi, and welcome to DIYAudio.

This is how to do it.

Click the image to open in full size.

Please keep in mind that +/- 40V is a bit much for a National chipamp. IIRC... 84 V is max for Overture Series. Don't forget to budget approximately 10% safety margin for mainline overvoltage fluctuations. When I lived in Anaheim (moved away in 99), we sometimes got overvoltages up to 176 volts!!! Could last for weeks at a time. Can't even begin to tell you how many appliances failed over the years, but I will say that my guitar equip was always blowing up. Since moving to Arkansas, haven't lost a single device. Line voltage here peaks at 124VAC during peak hours. Even with lightening storms of biblical proportions I've not lost a single appliance. I don't regret moving.
__________________
Writing is good exercize for the texticles!
  Reply With Quote
Old 11th November 2007, 11:18 AM   #3
Nordic is offline Nordic  South Africa
diyAudio Member
 
Nordic's Avatar
 
Join Date: Sep 2005
If it only has 3 leads for secondaries , it IS centre tapped, and you should use only one rectifier.
  Reply With Quote
Old 11th November 2007, 11:35 AM   #4
diyAudio Member
 
Join Date: Mar 2004
Location: Arkansas
Excuse me, I seem to have misread the original post. It suggests separate dual secondaries, and then a contradiction indicating it has three leads. I'm so easily confused my nickname is head_spaz.

Indeed Nordic is right IF you have only three leads on the secondary. One is a center tap (or an off-center tap, but that's kind of rare) and you'll need to incorporate a single bridge rectifier.

Audio sector.com, or Chipamp.com, or maybe both, provide instructions for using a CT transformer with their PSU boards.
Rather than search for the link, I'll just post a pic that I archived one day.

Click the image to open in full size.

Credit wherever credit is due... etc...

Hope this helps.
__________________
Writing is good exercize for the texticles!
  Reply With Quote
Old 12th November 2007, 01:48 AM   #5
glt is offline glt  United States
diyAudio Member
 
Join Date: Oct 2004
Thanks so much for the replies. The transformer is indeed dual secondaries but the secondaries are connected in series. I checked http://www.avellindberg.com/transfor...onnections.htm and indeed there is a configuration where the secondaries are in series.

I think the difference between CT and series secondaries is that in CT one side is half wave and the other side is half wave. In dual secondaries in series, both sides are full wave.

I did some more experiments changing the phase of the primaries (which are connected in parallel) and blew more fuses. So there is only one the only way to connect the primaries. I also experimented by changing the connections of the secondaries and I couldn't get the virtual grounds to be at the same voltage

So I think the transformer behaves like a CT transformer and only one bridge can be used. However, when I measure the voltage across the outer leads (not the "middle" lead), I get 60V AC (84VDC)

Not sure what's the purpose of such transformer, but I got it cheap and did not come with any kind of spec. It was an avel lindberg though... I guess I need to pay full price and get a "real" dual secondary transformer... Thanks again for the replies.
  Reply With Quote
Old 12th November 2007, 06:41 AM   #6
glt is offline glt  United States
diyAudio Member
 
Join Date: Oct 2004
Default Salvaged the transformer

Update: Just after giving up on using the transformer, I decided to open up the outer insulation and look inside. I then disconnected the two secondaries and soldered a separate wire to the other wire. Now I have a well behaved separate dual secondaries transformer. Patched it up with shrink tubing, scotch tape and some plastic sheets....
  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
Series wire Antek Secondaries pjanda1 Tubes / Valves 9 20th August 2009 02:17 PM
One transformer with 4 secondaries or two transformers with dual secondaries Baka Chip Amps 5 28th November 2008 06:39 AM
12V CT push-pull series secondaries eltonseemann Power Supplies 16 26th July 2007 03:35 PM
is it safe to connect these secondaries in series? jarthel Tubes / Valves 3 15th June 2007 12:28 PM
Center Tap vs Dual Secondaries StalfoS Chip Amps 6 18th March 2005 10:10 PM


New To Site? Need Help?

All times are GMT. The time now is 10:12 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