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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