[Elecraft] Walwarts - linear supplies
Jim Brown
jim at audiosystemsgroup.com
Tue Nov 21 03:43:37 EST 2017
On 11/20/2017 5:50 PM, Brian Hunt wrote:
> Be careful using the non-regulated linear wall warts. The open circuit voltage can be more than 16 VDC and could be harmful to gear not rated that high.
Yes and no. The vast majority of linear wall warts are UN-regulated,
but the current drawn by the equipment being powered significantly
reduces the output voltage, usually to the rated value. That's how
linear, unregulated power supplies work. That's why it's good to match
both rated voltage and current. AND -- most equipment will tolerate
moderate over-voltage. The K3, for example, is rated for 15VDC max.
And, or course, not all gear runs on 12VDC -- lots of stuff runs on 5V,
7.5V, 9V, and 14V.
> Best to measure OC first!
Measuring OC is a good thing, and EXPECT to see 25-30% higher voltage
than rated. But what matters is the voltage under load. And that's why
my applications note recommends putting Power Poles on both the wart and
the connector to the equipment, then sticking a voltage monitor in line
with the equipment connected. You did read the link I posted, didn't
you? :)
73, Jim K9YC
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