[Yaesu] radio shack 25 amp switcher?

[Eric Lemmon]

Bill,

If you're floating a battery across the output of a linear Astron
(RS-xx) power supply, and have not fried it yet, you've been lucky! 
Whether the power supply is a linear model or a switcher is not that
important.  What is very important is how the overvoltage protection
circuit works.  Most linear Astrons and some switchers use a "crowbar"
circuit to place a dead short on the output via an SCR when the voltage
exceeds a set amount.  This is good- unless there's a hefty battery
connected across the output!  I have seen several power supplies- not
just Astrons- get severely damaged during a power outage when the
battery voltage on the de-energized power supply looked like an
overvoltage, and caused the SCR to trip.

To prevent this unpleasantness, you can use a high-current Schottky
diode to isolate the battery from the power supply (remember to increase
the voltage setting to compensate for the forward voltage drop of the
diode), or you can disable the overvoltage crowbar circuit. 
Unfortunately, most manufacturers of switchers do not include a
schematic diagram.  One reason for that practice is that full AC line
voltage is present in much of the active circuitry, while in a linear
supply, the transformer provides a much lower operating voltage.

73, Eric Lemmon WB6FLY

Do you know if you can float a battery across it like I do my
transformer type Astron?? I like to have batts floated across mine so
when the power glitches (I live in Florida) I don't have to worry about
the voltage changing!!
> 
> 73, Bill N4XEO