On 8/22/2012 6:09 PM, Craig Franck wrote:
I am considering buying a DX-440 off someone for $40. It requires
a 9V 300mA AC adapter. The one with it is a 9.6V AC adapter. The
radio seems to work fine. I have a correct 9V adapter, but I was
wondering whether this should put me off the purchase because it
may have shortened the life of the radio.

Craig


The working voltage input to the radio is dependent on the load
capacity of the adaptor, and the draw of the radio. With an unregulated
adaptor, sufficient load will draw down the voltage input to the radio,
so if the adaptor's output is rated at 9v for that radio, the open
circuit voltage can be considerably higher. As much as 12v, in some
cases. So, when evaluating an unregulated adaptor, both the rated
current and rated voltage should be considered against the drain of the
radio.

The bad news is that if the adaptor is unregulated, and the capacity
is sufficiently large, that the voltage draw down will not be sufficient
to bring the voltage input to the radio down to the radio's specs. Most
radios, today, are diode protected so any reasonable overvoltage won't
harm the radio. If the radio is not diode protected, the overvoltage of
the adaptor when load is not sufficient can damage the radio.

My recommendation would be to see if the radio works on batteries. If
so, make the purchase. Life of the radio is rarely affected
incrementally by an over voltage, or an incorrect current. It's either
damaged, and stops working, or it's not and works properly. But don't
use the supplied adaptor. Find another one, either regulated at the
correct rated voltage, or unregulated at voltage and current ratings
that are correct for the radio.

DX-440, is a common enough radio that you'll be able to find a
correct adaptor easily.