I'm re-using transformers...

[~misfit~]

.... from old audio gear. I just want to check something as I'm not planning
on dying this week.

If the voltages I'm getting from the secondaries aren't what I want is it ok
to use the '120v' primary windings to get different voltages on the
secondaries?

Thanks,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Clifford Heath]

On 08/06/17 15:56, Phil Allison wrote:

~misfit~ wrote:
... from old audio gear. I just want to check something as I'm not planning
on dying this week.

If the voltages I'm getting from the secondaries aren't what I want is it ok
to use the '120v' primary windings to get different voltages on the
secondaries?
** If this is a mains power transformer, the operating frequency need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.

If the transformer has a 220V winding, he might be ok using that...
or not?

 

[Pete]

~misfit~ wrote:

is it ok
to use the '120v' primary windings to get different voltages on the
secondaries?

No, it's not okay to connect a 120v primary to 240v directly. What were
you hoping to do?

Depending on the rating of the transformer, and what kind of power
you're trying to draw, you might be able to use a mains-rated capacitor
in series with the primary to drop the voltage down from 240v to 120v,
but that only gives you the rated secondary voltage output, and I'm
guessing that's not what you want.

A transformer designed for 60hz might also run a bit hotter on 50hz.

Peter

 

[Phil Allison]

~misfit~ wrote:

----------------------

... from old audio gear. I just want to check something as I'm not planning
on dying this week.

If the voltages I'm getting from the secondaries aren't what I want is it ok
to use the '120v' primary windings to get different voltages on the
secondaries?

** If this is a mains power transformer, the operating frequency need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.



..... Phil

 

[Phil Allison]

Clifford Heath wrote:

------------------------

Phil Allison wrote:

** If this is a mains power transformer, the operating frequency need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


If the transformer has a 220V winding, he might be ok using that...
or not?

** Like Schrodinger's cat, only trying it out will prove the point.

It might run hot or make a lot of buzzing noise or both.

Beware if it is a toroidal type.


..... Phil

 

[Peter]

On 8/06/2017 5:29 PM, Phil Allison wrote:

Clifford Heath wrote:

------------------------

Phil Allison wrote:


** If this is a mains power transformer, the operating frequency need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


If the transformer has a 220V winding, he might be ok using that...
or not?


** Like Schrodinger's cat, only trying it out will prove the point.

It might run hot or make a lot of buzzing noise or both.

Beware if it is a toroidal type.


.... Phil

What should I beware of with toroidal types? I only ask because I have
one, 240V primary, 24V 0 24V secondary in a home built bench psu. It
seems to be working okay.

 

[Phil Allison]

Peter wrote:

-----------------

Phil Allison wrote:


** If this is a mains power transformer, the operating frequency need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


If the transformer has a 220V winding, he might be ok using that...
or not?


** Like Schrodinger's cat, only trying it out will prove the point.

It might run hot or make a lot of buzzing noise or both.

Beware if it is a toroidal type.



What should I beware of with toroidal types? I only ask because I have
one, 240V primary, 24V 0 24V secondary in a home built bench psu. It
seems to be working okay.

** But if you had one with a 220 V primary .....

The difference is the toroidal cores are different - there are air gaps at all to soften saturation AND the core goes sharply and HARD into saturation.

A toroidal designed for 60Hz operation is very often unusable at 50Hz.

Massive off load current draw - more than the full VA rating.



..... Phil

 

[~misfit~]

Once upon a time on usenet Phil Allison wrote:

~misfit~ wrote:

----------------------

... from old audio gear. I just want to check something as I'm not
planning on dying this week.

If the voltages I'm getting from the secondaries aren't what I want
is it ok to use the '120v' primary windings to get different
voltages on the secondaries?



** If this is a mains power transformer, the operating frequency need
to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is
driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.



.... Phil

Thanks Phil. It seems I need to read an 'into to transformers' type
tutorial.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Phil Allison]

~misfit~ wrote:

-------------------

** If this is a mains power transformer, the operating frequency need
to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is
driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


Thanks Phil. It seems I need to read an 'into to transformers' type
tutorial.

** You could do a lot worse than start here:

http://sound.whsites.net/xfmr.htm



...... Phil

--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Peter]

On 8/06/2017 8:59 PM, Phil Allison wrote:

Peter wrote:

-----------------


Phil Allison wrote:


** If this is a mains power transformer, the operating frequency need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


If the transformer has a 220V winding, he might be ok using that...
or not?


** Like Schrodinger's cat, only trying it out will prove the point.

It might run hot or make a lot of buzzing noise or both.

Beware if it is a toroidal type.



What should I beware of with toroidal types? I only ask because I have
one, 240V primary, 24V 0 24V secondary in a home built bench psu. It
seems to be working okay.


** But if you had one with a 220 V primary .....

The difference is the toroidal cores are different - there are air gaps at all to soften saturation AND the core goes sharply and HARD into saturation.

A toroidal designed for 60Hz operation is very often unusable at 50Hz.

Massive off load current draw - more than the full VA rating.



.... Phil

Mine is running within the specs stated on the sticker so it should be
okay then. Many thanks for the advice.

 

[~misfit~]

Once upon a time on usenet Phil Allison wrote:

~misfit~ wrote:

-------------------



** If this is a mains power transformer, the operating frequency
need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is
driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


Thanks Phil. It seems I need to read an 'into to transformers' type
tutorial.



** You could do a lot worse than start here:

http://sound.whsites.net/xfmr.htm

Excellent, thanks. I've bookmarked it and will read it as I am able.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[~misfit~]

Once upon a time on usenet Phil Allison wrote:

~misfit~ wrote:

-------------------



** If this is a mains power transformer, the operating frequency
need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is
driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


Thanks Phil. It seems I need to read an 'into to transformers' type
tutorial.



** You could do a lot worse than start here:

http://sound.whsites.net/xfmr.htm

I've also saved all three parts to my HDD. I'm a slow learner (learning
disability - I can only absorb so much at a time before getting hellacious
headaches) and in the past I've gone to read a bookmarked site only to find
it's no longer there. :-/

Thanks again.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[~misfit~]

Once upon a time on usenet ~misfit~ wrote:

Once upon a time on usenet Phil Allison wrote:
~misfit~ wrote:

-------------------



** If this is a mains power transformer, the operating frequency
need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core
is driven hard into saturation. The tranny will smoke and fuses
blow. So in general - no way.


Thanks Phil. It seems I need to read an 'into to transformers' type
tutorial.



** You could do a lot worse than start here:

http://sound.whsites.net/xfmr.htm

Excellent, thanks. I've bookmarked it and will read it as I am able.

Just FYI the reason I've been testing my salvaged transformers is because
I'm in need of a reasonable pre-amp as I've recently changed from using
integrated amps due to the decent speakers I now have that sound better and
better the more power they get. (Even at low volume. Powering them with a
~150w amp they sound much more detailed and image much better than powering
them with a 60w amp.)

However I can't afford the ~$1.5K a new preamp costs and despite watching
online auctions for a year haven't found anything suitable. (I need a
remote. Being an invalid it ruins my enjoyment of music if I have to keep
getting up to get the volume just right.) Funds are very very tight.

So, after trying various cheaper units from AliExpress which were
dissapointing I ordered one of these;
https://www.aliexpress.com/item/PGA2311-Volume-Stereo-Pre-amplifier-Preamp-Board-with-LCD-and-Remote-control/1695574309.html
and figure that, if it sounds good when I have the funds I'll then get one
of these to house it;
https://www.aliexpress.com/item/New-Version-aluminum-Case-for-PGA2311-CS3310-Preamp/32809522765.html

However on going through my collection of centre tapped transformers
salvaged from various things the only 6v-0-6v transformer I was able to find
was from an old digital alarm clock (and is actually 6.0 - 0 - 6.3v) but I
reckon it's only capable fo supplying about 2 watts - which likely isn't
enough. I have a bunch that are 12 - 0 -12 and a few from amplifiers going
right up to 75 - 0 - 75.

Ultimately, after my first post inthis thread I ended up ordering one of
these in 6 - 0 - 6 configuration;
https://www.aliexpress.com/item/1-10W-EI-Ferrite-Core-Input-220V-50Hz-Vertical-Mount-Electric-Power-Transformer-Leave-A/32799457326.html
for another ~NZ$20.

I'll assmeble it on a board when I get these two parts and see how it
sounds. If it's good I'll then try to find the ~NZ$90 for the case.

However now I've had to buy a transformer I'm starting to think I should
have just bit the bullet and bought the pre-built unit;
https://www.aliexpress.com/item/Finished-PGA2311-Remote-Pre-amplifier-Preamp/32809614146.html

Anyway fingers crossed, I've already wasted about $50 buying several cheaper
pre-amps. I have one that sounds pretty damn good but it's not got a remote
and is single input. Adding a motorised pot and control circuitry and
switchable inputs to that might cost as much or more and still be a fail
(with my limited skills).

Cheers,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Ian Field]

"Pete" <pjetson@yahoo.com> wrote in message
newshanvv$pdl$1@dont-email.me...

~misfit~ wrote:
is it ok
to use the '120v' primary windings to get different voltages on the
secondaries?

No, it's not okay to connect a 120v primary to 240v directly. What were
you hoping to do?

Depending on the rating of the transformer, and what kind of power you're
trying to draw, you might be able to use a mains-rated capacitor in series
with the primary to drop the voltage down from 240v to 120v, but that only
gives you the rated secondary voltage output, and I'm

Not the best idea - if you accidentally hit series resonance, things start
to happen.................................

 

[~misfit~]

Once upon a time on usenet Phil Allison wrote:

~misfit~ wrote:

-------------------



** If this is a mains power transformer, the operating frequency
need to be double if you do that. 100Hz instead of 50Hz.

If not, then the primary current will be massive as the iron core is
driven hard into saturation. The tranny will smoke and fuses blow.

So in general - no way.


Thanks Phil. It seems I need to read an 'into to transformers' type
tutorial.



** You could do a lot worse than start here:

http://sound.whsites.net/xfmr.htm

Phil quick question (as I can't readily find the answer right now).

Can I use a transformer with the primary side described as 'double 120v
50/60Hz' on 240v by running the two primaries in series?

Cheers,
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Phil Allison]

~misfit~ wrote:

-----------------

Phil quick question (as I can't readily find the answer right now).

Can I use a transformer with the primary side described as 'double 120v
50/60Hz' on 240v by running the two primaries in series?

** Errr - that is how it is meant to be used.

In parallel for 120VAC, in series for 240VAC.

You WILL need a to get the phasing right, hopefully the units are marked or you have an info sheet showing which wire colours to join.



..... Phil

 

[~misfit~]

Once upon a time on usenet Phil Allison wrote:

~misfit~ wrote:

-----------------


Phil quick question (as I can't readily find the answer right now).

Can I use a transformer with the primary side described as 'double
120v 50/60Hz' on 240v by running the two primaries in series?




** Errr - that is how it is meant to be used.

I thought so as it makes sense but I haven't read that anywhere and the site
selling them doesn't say that.

> In parallel for 120VAC, in series for 240VAC.

Makes sense.

You WILL need a to get the phasing right, hopefully the units are
marked or you have an info sheet showing which wire colours to join.

Hopefully. I haven't ordered yet but AliExpress isn't known for giving out
lots of info. :-/

Thanks for replying.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Ian Field]

"Phil Allison" <pallison49@gmail.com> wrote in message
news:bac19a87-12a1-4518-8f89-bc84fdd77de2@googlegroups.com...

~misfit~ wrote:

-----------------


Phil quick question (as I can't readily find the answer right now).

Can I use a transformer with the primary side described as 'double 120v
50/60Hz' on 240v by running the two primaries in series?




** Errr - that is how it is meant to be used.

In parallel for 120VAC, in series for 240VAC.

You WILL need a to get the phasing right, hopefully the units are marked
or you have an info sheet showing which wire colours to join.

In series - wrong phasing just doesn't work.

In parallel - wrong phasing lets the magic smoke out.

 

[Ian Field]

"~misfit~" <shaun.at.pukekohe@gmail.com> wrote in message
newshqll7$krj$1@dont-email.me...

Once upon a time on usenet Phil Allison wrote:
~misfit~ wrote:

-----------------


Phil quick question (as I can't readily find the answer right now).

Can I use a transformer with the primary side described as 'double
120v 50/60Hz' on 240v by running the two primaries in series?




** Errr - that is how it is meant to be used.

I thought so as it makes sense but I haven't read that anywhere and the
site selling them doesn't say that.

In parallel for 120VAC, in series for 240VAC.

Makes sense.

You WILL need a to get the phasing right, hopefully the units are
marked or you have an info sheet showing which wire colours to join.

Hopefully. I haven't ordered yet but AliExpress isn't known for giving out
lots of info. :-/

Series won't do anything if you get the phase wrong. Power up parallel with
a light bulb in series to limit the current in case you got it wrong.

 

[Phil Allison]

Ian Field wrote:

--------------------

** Errr - that is how it is meant to be used.

In parallel for 120VAC, in series for 240VAC.

You WILL need a to get the phasing right, hopefully the units are marked
or you have an info sheet showing which wire colours to join.


In series - wrong phasing just doesn't work.

In parallel - wrong phasing lets the magic smoke out.

** Nonsense, the situations are both the same.

One half of the primary is trying to magnetise the core in the opposite direction to the other. So the core does not magnetise, there is no back emf - leaving only the resistance of the windings.

You are thinking of the situation with split *secondaries*.


...... Phil