I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Thanks for any suggestions.

The Revd wrote:
I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Thanks for any suggestions.

Why do you think the rectifier EXISTS?
The lamp doesn't care whether it's ac or dc. At
least the first order effects don't care.
It should be a tiny bit happier with AC.

On Tue, 12 Jul 2011 08:58:04 -0700, mike wrote:

The Revd wrote:
I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Thanks for any suggestions.

Why do you think the rectifier EXISTS?
The lamp doesn't care whether it's ac or dc. At
least the first order effects don't care.
It should be a tiny bit happier with AC.

I assumed that a 12V halogen bulb would take DC voltage. Am I wrong?
The lamp stopped working, the bulb is OK (continuity fine, at least).

I assumed that a 12V halogen bulb would take DC voltage. Am I wrong?

Probably.

Something's odd, though. If you've got 12V from the transformer, but the
light won't light, you need to do more troubleshooting.

On Tue, 12 Jul 2011 09:25:01 -0700, "William Sommerwerck"
wrote:

I assumed that a 12V halogen bulb would take DC voltage. Am I wrong?

Probably.

Something's odd, though. If you've got 12V from the transformer, but the
light won't light, you need to do more troubleshooting.

My apologies. Turns out the output socket on the transformer was
cooked and I'll have to bypass it.

mike wrote:
The Revd wrote:
I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Thanks for any suggestions.

Why do you think the rectifier EXISTS?
The lamp doesn't care whether it's ac or dc. At
least the first order effects don't care.
It should be a tiny bit happier with AC.

Probably to reduce the total power to the bulb, to make it less bright. A cheap
way of implementing off/low/high.

Geoff.



--
Geoffrey S. Mendelson N3OWJ/4X1GM
Making your enemy reliant on software you support is the best revenge.

Geoffrey S. Mendelson wrote:
mike wrote:
The Revd wrote:
I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Thanks for any suggestions.
Why do you think the rectifier EXISTS?
The lamp doesn't care whether it's ac or dc. At
least the first order effects don't care.
It should be a tiny bit happier with AC.

Probably to reduce the total power to the bulb, to make it less bright. A cheap
way of implementing off/low/high.
OK, but the diode would get shorted on high, so don't think that's the
issue.
AC is present and should light the light.

Geoff.

On Jul 12, 8:58*am, mike wrote:
The Revd wrote:
I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Thanks for any suggestions.

Why do you think the rectifier EXISTS?
The lamp doesn't care whether it's ac or dc. *At
least the first order effects don't care.
It should be a tiny bit happier with AC.

Somebody should know how the redeposition of tungsten from the halogen
interacts with the different notching patterns created by DC and AC
currents.

"The Revd" wrote in message
...
On Tue, 12 Jul 2011 08:58:04 -0700, mike wrote:

The Revd wrote:
I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Thanks for any suggestions.

Why do you think the rectifier EXISTS?
The lamp doesn't care whether it's ac or dc. At
least the first order effects don't care.
It should be a tiny bit happier with AC.

I assumed that a 12V halogen bulb would take DC voltage. Am I wrong?


If you run a lamp on DC the almost molten tungsten gradually migrates to one
end of the filament leaving weak spots at the other end where it becomes
thinner - this shortens lamp life compared to running on AC.

On Tue, 12 Jul 2011 11:52:46 -0400, The Revd
wrote:

I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Nope. The first overvoltage power glitch will blow the bulb.

The blown module is *NOT* a transformer and rectifier. You probably
have a module with a 12V output switching power supply inside. They
like to fail. The problem is that something got lost in the
translation from Chinese to English, resulting in these switchers
being labeled as "transformers". For example:
http://www.dhgate.com/10x-12v-mr16-halogen-lamp-power-supply-transformer/r-ff8080812d0dad01012d0e4aeade785d.html
is labeled an "electronic transformer". It's not. It's a switching
power supply. However, since it does transform 117vAC to 12vDC, I
guess it could be considered a type of transformer.

You should be able to read the label on the switcher to find a
replacement. If not, obtain the power rating of the halogen bulb in
watts, and search for a "XX watt halogen lamp transformer".


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 12 Jul 2011 12:03:40 -0400, The Revd
wrote:

I assumed that a 12V halogen bulb would take DC voltage. Am I wrong?
The lamp stopped working, the bulb is OK (continuity fine, at least).

They intentionally run on DC. This article explains some of it:
http://www.radiolocman.com/shem/schematics.html?di=28080
http://www.rlocman.ru/i/File/2007/05/07/EL_transf_12V.pdf
Quoting:
The "electronic" transformer represents an alternative means of
power conversion to the more standard iron core, 50 Hz transformer
technique. The advantages of the electronic transformer compared
with the classical solution a
- The output power from the electronic transformer to the
lamp can be varied, thus dimming control can be added;
- It is possible to include protection against short
circuit of the lamp filament;
- Weight can be reduced and the construction made more compact;
- Acoustic noise (mains hum) is eliminated.

In addition, if you've ever watched an AC driven light bulb filament
on a high speed camera, the filament vibrates slightly at 60Hz. This
is not a problem when the filament is fairly thin, flexible, and cool.
However, doing the same at the higher temperatures of a halogen bulb
will vibrate the stiff filament until it breaks.

DC rules. Edison was right and Tesla was wrong.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 12 Jul 2011 14:49:18 -0700, Jeff Liebermann
wrote:

On Tue, 12 Jul 2011 12:03:40 -0400, The Revd
wrote:

I assumed that a 12V halogen bulb would take DC voltage. Am I wrong?
The lamp stopped working, the bulb is OK (continuity fine, at least).

They intentionally run on DC.

Oops. I goofed. The halogen bulbs run on AC. Looks like it will
work with just a transformer with no diode required.

Sorry(tm).
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 12 Jul 2011 14:37:20 -0700, Jeff Liebermann
wrote:

On Tue, 12 Jul 2011 11:52:46 -0400, The Revd
wrote:

I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Nope. The first overvoltage power glitch will blow the bulb.

Which was my experience with various utility lamps running halogen
bulbs. The slightest power glitch blew the bulb. In my case, it was
a glitchy emergency generator.

However, I was wrong. The electronic transformer really is an AC to
AC transformer, not AC to DC. Sorry for the mistake.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 12 Jul 2011 15:17:48 -0700, Jeff Liebermann
wrote:

On Tue, 12 Jul 2011 14:37:20 -0700, Jeff Liebermann
wrote:

On Tue, 12 Jul 2011 11:52:46 -0400, The Revd
wrote:

I have a halogen lamp from IKEA with a 120V to 12V transformer.
The rectifier (presumably) has failed and the transformer is
outputting 12V AC instead of 12V DC.

Can I wire in a generic rectifier to the output side to solve the
problem?

Nope. The first overvoltage power glitch will blow the bulb.

Which was my experience with various utility lamps running halogen
bulbs. The slightest power glitch blew the bulb. In my case, it was
a glitchy emergency generator.

However, I was wrong. The electronic transformer really is an AC to
AC transformer, not AC to DC. Sorry for the mistake.

Many thanks for the info. As posted earlier, it turned out the
transformer output socket was cooked. And, when this was fixed (or
rather bypassed), it turned out the toggle switch on the bulb holder
was also cooked :-)

"Ian Field" writes:



If you run a lamp on DC the almost molten tungsten gradually migrates to one
end of the filament leaving weak spots at the other end where it becomes
thinner - this shortens lamp life compared to running on AC.


Flip the lamp in the socket monthly, maybe?


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"David Lesher" wrote in message
...
"Ian Field" writes:



If you run a lamp on DC the almost molten tungsten gradually migrates to
one
end of the filament leaving weak spots at the other end where it becomes
thinner - this shortens lamp life compared to running on AC.


Flip the lamp in the socket monthly, maybe?

The migration is extremely lumpy so you still get weakened spots on the
relatively thicker sections of the filament, and I vagely remember the book
I read years ago explaining why reversing the DC doesn't help as much as
you'd expect - unfortunately I can't remember what that explanation was.

"Ian Field" wrote in
:


"David Lesher" wrote in message
...
"Ian Field" writes:



If you run a lamp on DC the almost molten tungsten gradually migrates
to one
end of the filament leaving weak spots at the other end where it
becomes thinner - this shortens lamp life compared to running on AC.


Flip the lamp in the socket monthly, maybe?

The migration is extremely lumpy so you still get weakened spots on
the relatively thicker sections of the filament, and I vagely remember
the book I read years ago explaining why reversing the DC doesn't help
as much as you'd expect - unfortunately I can't remember what that
explanation was.




if the lamp has a transformer,why is the bulb running on DC?
transformers output AC.
you would have to add an extra component(diode) at more cost,and for lesser
performance.

Or is the "transformer" actually a AC-DC switching converter?
I have a LED gooseneck desk lamp that has an AC-DC switching converter,in
the line plug.

--
Jim Yanik
jyanik
at
localnet
dot com

"Jim Yanik" wrote in message
4...
"Ian Field" wrote in
:


"David Lesher" wrote in message
...
"Ian Field" writes:



If you run a lamp on DC the almost molten tungsten gradually migrates
to one
end of the filament leaving weak spots at the other end where it
becomes thinner - this shortens lamp life compared to running on AC.


Flip the lamp in the socket monthly, maybe?

The migration is extremely lumpy so you still get weakened spots on
the relatively thicker sections of the filament, and I vagely remember
the book I read years ago explaining why reversing the DC doesn't help
as much as you'd expect - unfortunately I can't remember what that
explanation was.




if the lamp has a transformer,why is the bulb running on DC?
transformers output AC.
you would have to add an extra component(diode) at more cost,and for
lesser
performance.

Or is the "transformer" actually a AC-DC switching converter?


All the electronic 'transformers' I've looked inside had a circuit
remarkably similar to a CFL - except no ballast coil and the primary of a
toroidal transformer is half bridge style between the O/P & divider
capacitors.

AFAICR I've never seen one with a secondary side rectifier.

It just happened that someone suggested DC operation and I'm one of those
pointing out that it wouldn't provide optimum lamp life.

David Lesher wrote:
"Ian Field" writes:



If you run a lamp on DC the almost molten tungsten gradually migrates to one
end of the filament leaving weak spots at the other end where it becomes
thinner - this shortens lamp life compared to running on AC.


Flip the lamp in the socket monthly, maybe?


Flip it 50 or 60 times per second, that will do.