Wall wart output voltages seem high

[JuiceKing]

Hi,

Like many of us, I have an extensive collection of wall warts, but before plugging them into non-matched equipment, I thought I'd check voltages.

The few that I'd like to use more seem quite high and it makes me concerned about using them in other equipment.

For example, a 6V-rated one (no brand) outputs 9.96V, and the 9V one (Sony-brand) outputs 11.87V. Both are pretty big and heavy, so I think they have linear PSUs inside.

Is it normal to have such output voltage? Are they expected to drop under load?

- Ken

[T4P]

That would mean they are unregulated. They only put out rated voltage at max current.

Whether you can use it or not depends on your equipment, if it can handle 12v at connection. Like example for a 9V pack
Small transformers usually have terrible regulation and even those old ones from panasonic i found are so poor they put out 17V when their rated voltage is 9V 

[Flávio V]

It is one of the reasons than i am planing to replace all of my house's supplies with some custom made switched ones...and i am not  going to talk about efficiency...than are normally near 30-60%..

[JuiceKing]

Makes perfect sense. Thanks!

- Ken

[Jon Chandler]

For perhaps more than you want to know, check out my article: AC-DC Power Supplies - Using Wall Warts

[Mint.]

Shouldn't you put a load on the supply first?

[JuiceKing]

Jon,  fantastic tutorial...answered all my questions and then some. Thank you!

[Jon Chandler]

Thanks for the kind remarks Ken.