The ones I measured just a couple of months ago were way too small and
light to have a transformer in them, and they were horrible. In any
case, I recommend that anyone using a wall wart for other than its
intended equipment (or any standalone new one) be sure to check it for
both noise and no load voltage regulation. It's quick and easy to do
and could save a lot of headaches.
73,
Dave AB7E
On 12/2/2023 9:09 PM, Victor Rosenthal 4X6GP wrote:
This is usually true of the linear type of wall-wart, which is the
quiet kind! They generally are composed of just a transformer,
rectifier, and capacitor.They are almost extinct these days, but I
look for discarded ones for use with equipment for which it is safe to
use an unregulated power source.
The switching types mostly are well-regulated, but of course they are
often noisy.
73,
Victor, 4X6GP
Rehovot, Israel
formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 03/12/2023 5:33, David Gilbert wrote:
Most of them have almost no reliable voltage regulation either. They
are typically designed for a certain load, and if they don't see that
load the voltage is much higher than rated. I've tested dozens of
these things (I tend not to throw anything away) and it's fairly
typical that a 12 volt rated wall wart power supply presents 16 to 18
volts (or higher) no load. That can be death to a piece of 12 volt
gear that doesn't draw much current.
Dave AB7E
On 12/2/2023 8:25 PM, Jim Brown wrote:
99.9% of stuff that plugs into the wall has a Switch-mode power
supply, most of which are varying degrees of noisy. They were
mandated to save energy about 20 years ago, but thanks to small
government, the FCC has no money to enforce their Rules that they be
quiet. So they aren't.
A typical home has several dozen of them, either in the form of wall
warts and line lumps or built into equipment and appliances. Rather
than buying bigger and better anything for our station, our time and
money is far better spent identifying and replacing as many as
possible of these nasty noise sources.
There's a tutorial on my website, k9yc.com/publish.htm about how to
find and replace them. All of the 12V gear in my shack runs on two
big batteries that are float charged by re-purposed Thinkpad power
supplies using Genasun charge regulators. A 100Ah LiFePO4 runs the
rigs, a 100Ah Sealed Lead Acid runs the rest of the stuff.
73, Jim K9YC
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