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How do I check a 12V AC Transformer?

I have an overhead, ceiling-mounted,.tracklighting system which consists of six 35W Halogen lights on a 9-foot track with a canopy type, in-line transformer which is marked: I/P: AC120V-60Hz 1.5A, O/P: AC 12V 50-230W. Been working fine for 2 years but suddenly died. After making sure all connections were tight and of course checking the AC input side (which was OK) I removed the transformer which contains 2 wires (black/white) going in and 2 wires (Red, larger gauge) coming out. I just don't know how to check the output of the transformer to see if I'm getting 12VAC out? Do I just put my test probes across the two red wires? Or one at a time to a ground? Can anyone help me on this. Thank you very much. (As you can see, I know very little about electronics!)

Reply to
Tony
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On Fri, 22 Dec 2006 14:47:40 -0800, Tony Has Frothed:

Across the two red leads.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794
Reply to
Meat Plow

Just put your meter across the two red output wires. Don't be surprised if this shows as more than 12V AC. That would be normal. I am guessing that if you disconnect the transformer completely and check the wires using your meter on resistance range, the output would seem fine but you would get no reading from the input.

Reply to
Colin

Thank you very much for your quick reply! I just did exactly that and I got a reading of

00.43 v

What the heck does that mean? thanks much

Reply to
Tony

On Fri, 22 Dec 2006 15:18:12 -0800, Tony Has Frothed:

Well if the black and white wires are hooked up to 120 volts it means the transformer is bad. But make sure your meter was on AC volts not DC.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794
Reply to
Meat Plow

It's probably a switchmode power supply rather than a transformer, they do tend to fail suddenly when they go.

If you have 120V in, the bulbs show continuity, and they don't light, the transformer is bad.

Reply to
James Sweet

On Sat, 23 Dec 2006 07:21:15 +0000, James Sweet Has Frothed:

Why would it need to be an SMPS and why would it fail more suddenly when it goes compared to just a plain old transformer? I would ASSume that since it needs to deliver 210 watts just a plain old tranformer would be cheaper than an SMPS hence more profit for the manufacturer :)

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794
Reply to
Meat Plow

210W at 12V is a *big* transformer, that's close to 20A. A transformer of that capacity would be very bulky and expensive, most equipment these days uses switchmode supplies because they're in fact much cheaper, they use a lot less copper and iron. The SMPS that halogen fixtures use are very cheap, they're more like light dimmers and put out a nasty waveform that looks like 12V to an incandescent load.

Magnetic transformers will often smell bad for a while as the winding insulation breaks down and turns short. SMPS fail suddenly when a component shorts.

Reply to
James Sweet

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