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

[Don Wilhelm]

  David,

I have many times commented negatively on the use of unregulated wall 
warts for use with any radio because the no load (low load) voltage can 
be substantially greater than the rated voltage (the specified voltage 
is only at full load).  Many 12 volt wall warts will develop 17 volts or 
more at no load.  Those power supplies intended for laptop computers may 
do the job, but still, I shudder at using them unmodified, and that does 
not speak to any potential spurious responses (some call them "birdies") 
coming from the power supply.

Regulated wall warts are a different matter (birdies not considered) - 
if they will provide the required current at 13.8 volts or so, then 
there is no harm in using them, but the availability of  13.8 volt 
regulated wall-warts is close to zero at the sources I normally use - it 
seems all the available ones with sufficient current that I have located 
are unregulated.

Use wall-warts and computer power supplies at your own peril.  For me, I 
would not subject any radio to such a power source.  With the K3 in 
particular, if one has spent upwards of $1.5k for the radio, then why 
"go cheap" on the power source.  Spend a few extra dollars and obtain a 
good 13.8 volt power supply - you will be more satisfied in the long run.

73,
Don W3FPR

On 5/10/2011 9:04 PM, David Gilbert wrote:
> 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
>