mc wrote:

"Joe Smith" wrote in message
...

I have a mains adaptor (marked as "model SPN 4079A") which is made in
the UK and which is marked ... "OUTPUT 12.5v 400mA".

I plugged it in the mains here in the UK and measured the voltage at
the end with the round concentric applicance plug. It was about 17.3
volts!


What you are seeing is quite normal for an unregulated adapter. Use it with
a load of 300 to 400 mA and you'll get the right voltage.


Not true!
*All* unregulated "wallwarts" have an output voltage higher than the
"spec" even at full load.
Measure some and find out for yourself.