Wall wart

You don't want to hear the whole complicated answer, but the answer is "maybe." Some are simple transformers (the ones that have A-C outputs.) The D-C version MAY have regulators and other electronic stuff that depends upon load to set the correct output. A little experimentation with a voltmeter and a few loads will help you figure it out.

The simple answer is with a load.  The more complicated answer is what Arthur said...  But I will add that regardless of what sort of wall wart you are testing, it should meet the specs printed on it.

The only thing I use a wall wart for on my layout is the DC output for my AC volt meter...

Tony

Stuff like cell phone chargers usually are regulated.  However, many other wall-warts are unregulated.  All you need to do is check the voltage with no load.  If your 9V wall-wart is showing around 12-13 volts, it's unregulated.  If it is showing 9V, it's regulated.

Thank you Gunner, that is what I thought.  I have a 12VDC powrer pack @1,000ma that I wantet to us for LED lights but when tested with no load it goes up to 15VDC.  Time to trash it.

Ken M

Well, just don't use it if you need a regulated 12V.   I keep them all, you'd be surprised as time goes by what you suddenly find a use for.

"I keep them all, you'd be surprised as time goes by what you suddenly find a use for."

Sir, would you kindly contact my wife aka Mrs. Throwitout, and repeat that remark? 

As soon as mine gets the word Arthur!

Ken M posted:

Thank you Gunner, that is what I thought.  I have a 12VDC powrer pack @1,000ma that I wantet to us for LED lights but when tested with no load it goes up to 15VDC.  Time to trash it

Ken M

Just run it through a cheap step down regulator, then it can be whatever voltage below that you need