On Fri, 3 Dec 2010 15:45:16 -0800 (PST), Mycroft668
wrote:

On Dec 3, 3:35*pm, PeterD wrote:
On Fri, 3 Dec 2010 08:01:53 -0800 (PST), Mycroft668





wrote:
On Dec 1, 8:48 am, PeterD wrote:
On Tue, 30 Nov 2010 07:55:30 -0800 (PST), wrote:
... I know there are transformers that do not
produce output unless under load

Now that's funny! Must be describing those new chinese intelegent
transformers, right?

I'm not sure if you are joking. There really are such things and I
found out the embarrassing way.
I was installing a fancy pendant light and there was a problem in the
wiring. Long story short, I checked the transformer and got almost no
output so I was sure it was defective. I called the supplier and he
told me the transformer didn't output current unless under load. I was
sure he was wrong never having heard of such a thing but after finding
and fixing the short which caused the light not to go on, the
transformer worked perfectly. *Always something new to learn just when
I think I have a full grasp of something!

Mycroft

You sure that light fixture wasn't using a switching power supply? A
transformer is a passive device, it doesn't know whether there is a
load or not, it just transforms one voltage to another.

No, I'm not sure. There was a little transformer-like box that went in
the electrical box

---
By "electrical box" do you mean a mains receptacle?
---

and the supplier said he gets calls like mine all
the time. (If the directions were better, he wouldn't be bothered so
much but that's another story)

I'm sure you know more than I and sorry if I was wrong. I DO know I
put a tester on one of the transformers I have (output 12VDC 2amp) and
there was a near zero reading,

---
Since the output of a transformer is AC, if you mistakenly thought it
was DC and used one of the DC ranges of your tester to try to measure
its output voltage, near-zero is what you'd read.
---

but it worked the light just fine
except for the slight flicker. I ALSO am sure he told me it wouldn't
have an output unless under load.

---
It wouldn't output _current_ unless it was loaded because it would be
driving an open circuit.

However, if you were to measure the AC voltage across its output
terminals you'd read something.
---

Come to think of it, they are
halogen lights. I don't know why they would need a unit in the
electrical box.

---
Probably because they're designed to run on something other than the
raw mains voltage, which the transformer converts into what the lamp
needs.

---
JF