Power supply issue

For the three and more legged things
Daniel Quinn
Old Hand
Posts: 858
Joined: Thu Jan 05, 2017 9:19 am

#1 Power supply issue

Post by Daniel Quinn »

I have a phono amp which requires two + power supply rails .

The power supply is configured with yellow and black going to + on separate bridge rectifiers . And the dc+ rail of the br connecting to plus on separate capacitors.

The capacitors have linked ~ terminals . The orange and red wires of the transformer are soldered to the copper bar connecting the negative terminals of capacitor .

I would expect this to give me 2 positive rails at approx 26v

One is as expected the other is only 8v

Anybody know why?
User avatar
pre65
Amstrad Tower of Power
Posts: 21367
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#2 Re: Power supply issue

Post by pre65 »

No.

But, as we have mentioned before, a diagram might make things more clear.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Nick
Site Admin
Posts: 15694
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#3 Re: Power supply issue

Post by Nick »

Generally I would expect the transformer to be connected to the AC terminals of the bridge. As Phil said try and draw what you have.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
rowuk
Old Hand
Posts: 453
Joined: Sun Jun 01, 2014 2:50 pm
Location: Germany

#4 Re: Power supply issue

Post by rowuk »

With the rectifiers disconnected, what AC voltages are at the transformer? I had a similar issue many years ago with an incorrectly labelled transformer. There was 0, 9 and 14 volts measured, the label said 15, 0, 0,15. With 9VAC going to the one side and 14VAC going to the other side of the rectifier, 8VDC volts is all that I got...
Whenever I feel blue, I start breathing again.
Daniel Quinn
Old Hand
Posts: 858
Joined: Thu Jan 05, 2017 9:19 am

#5 Re: Power supply issue

Post by Daniel Quinn »

I’ll try rephrasing

I’ve got a transformer with 2 secondaries

I’ve got my 2 ac secondaries attached to the + side of two separate bridge rectifiers . They both show 18v ac n accordance with the specs .

Measuring the separate bridge rectifiers at the dc terminal I’ve got one showing 26v and one showing 8v

I’ve got the 0v for both secondaries attached to a copper bar which is attached at each end to a separate capacitor .

Why are both + terminals not showing 26v , something wrong or electrical law are not privy to?

Also anybody have examples of power supply with two 24v positive rails?
User avatar
pre65
Amstrad Tower of Power
Posts: 21367
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#6 Re: Power supply issue

Post by pre65 »

Something wrong.

Seems connecting the two secondary's to two bridges should be OK, if you have the wires in the right place, but how do you get the 0v connection ?

Is the transformer 0-18v + 0-18v ?

Still need a diagram to make full sense of what you are doing.
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
IslandPink
Amstrad Tower of Power
Posts: 10041
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

#7 Re: Power supply issue

Post by IslandPink »

Daniel Quinn wrote: Sun Jul 31, 2022 12:58 pm I’ve got my 2 ac secondaries attached to the + side of two separate bridge rectifiers .
Why are they not attached to the ~ and ~ terminals ?
"Once you find out ... the Circumstances ; then you can go out"
User avatar
Nick
Site Admin
Posts: 15694
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#8 Re: Power supply issue

Post by Nick »

Don't try rephrasing just draw a simple picture.

As close as I can make out from your text the transformer should not be connected to the + on the bridge rectifier.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
User avatar
Nick
Site Admin
Posts: 15694
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#9 Re: Power supply issue

Post by Nick »

Last try. Is there any reason other than trying to bend us to your will that is stopping you from posting a simple diagram?
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
Daniel Quinn
Old Hand
Posts: 858
Joined: Thu Jan 05, 2017 9:19 am

#10 Re: Power supply issue

Post by Daniel Quinn »

I’ve still not figured how to do it and was being lazy .

The reason I have not used the negative terminal on the bridge is because I need two positive 26v
User avatar
shane
Social outcast
Posts: 3400
Joined: Sun Sep 16, 2007 12:09 pm
Location: Kept in a cool dry place.

#11 Re: Power supply issue

Post by shane »

Daniel Quinn wrote: Sun Jul 31, 2022 12:58 pm I’ve got my 2 ac secondaries attached to the + side of two separate bridge rectifiers
This is the bit I’m struggling with. In my (very limited) experience, a bridge rectifier has two AC terminals, sometimes marked ~, which connect to each end of the transformer secondary, and a + and a - terminal for the DC output. If you have two secondaries and two rectifiers it would often be the case that the two DC - terminals are connected to the same earth bar, but I can’t understand why you would connect either end of the secondary to the + terminal.

As everyone keeps saying, a diagram of what you have would really help!
The world looks so different after learning science. For example, trees are made of air, primarily. When they are burned, they go back to air, and in their flaming heat is released the flaming heat of the Sun which was bound in to convert air into tree.
User avatar
pre65
Amstrad Tower of Power
Posts: 21367
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#12 Re: Power supply issue

Post by pre65 »

How to wire a bridge rectifier.

The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
Daniel Quinn
Old Hand
Posts: 858
Joined: Thu Jan 05, 2017 9:19 am

#13 Re: Power supply issue

Post by Daniel Quinn »

I know how to wire a bridge rectifier ! But you wire it normally and you get a + rail and a negative rail . This works fine for the vast majority of applications .

I need a power supply with two plus rails at 26v .
User avatar
pre65
Amstrad Tower of Power
Posts: 21367
Joined: Wed Aug 22, 2007 11:13 pm
Location: North Essex/Suffolk border.

#14 Re: Power supply issue

Post by pre65 »

For fuck sake, just do a diagram if you really want our help.

How hard can it be ? :?

Just a rough diagram showing connection points and wire colours will do.

Again, how are you configuring the 0v connection ?
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
User avatar
Nick
Site Admin
Posts: 15694
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

#15 Re: Power supply issue

Post by Nick »

Daniel Quinn wrote: Sun Jul 31, 2022 2:47 pm I know how to wire a bridge rectifier ! But you wire it normally and you get a + rail and a negative rail . This works fine for the vast majority of applications .

I need a power supply with two plus rails at 26v .
Well just do what you know to do twice.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
Post Reply