[Elecraft] K3 - How much supply voltage is too much?

[David Gilbert]

Didn't someone here not too long ago post some information on the 
unreliable voltage regulation of many wallwart/laptop supplies?   Maybe 
it wasn't this reflector.  In general, though, I believe the thread 
mentioned that many of those supplies assume a load, and under no load 
conditions the voltage often went up several volts.  The K3 has it's own 
internal voltage regulators, but I'm not sure I'd want to subject them 
to that sort of over voltage at turn on.

Dave   AB7E



> On 5/10/2011 15:32, Brian Alsop wrote:
>> Roger,
>>
>> You should see the crummy "DC" waveforms put out by typical laptop
>> switching supplies.  I bought a bunch at a recent hamfest.  Put each one
>> on a 'scope to observe the output.  One had a 0.5 volt sawtooth
>> superimposed over the DC value.  Another have ringing with introducing a
>> swing of over a volt in magnitude around the DC value.  I tested at zero
>> and full load.  None of these problems went away.  The rest were far
>> from clean.  Some were IBM branded.
>>
>> No way would I put my rig on one of these beasties.
>>
>> I don't know how laptops manage to tolerate them.
>>
>> The only other thing is yes were hamfest items and could have all been
>> rejects or something.
>>
>> For what it is worth,  I did find one good supply but it was for a Kodak
>> printer.  However, it put out 25 volts.   The output was very clean at
>> all levels of load.
>>
>> 73 de Brian/K3KO