[Elecraft] queer behaviour !

[Guy Olinger K2AV]

Have seen a K3 with toasted circuitry due to trying to key -150 volts.
 Don't do it.  Damage requiring component replacement is definitely
possible.

73, Guy.

On Wed, Aug 18, 2010 at 7:59 AM, Paul Christensen <w9ac at arrl.net> wrote:
> The K3's KEY OUT jack is rated at +200V @ 5A.  I owned an SB-230 back in the
> mid '70s and I believe it uses a relatively HV negative key line.  So, while
> the K3's keying circuit is very robust for positive key lines, it acts as a
> short on negative key lines.  I doubt any damage has been done to the K3,
> despite the high negative key line of the SB-230 amp.
>
> The Jackson Harbor Press "Keyall" uses a pair of HV MOSFETs, floating above
> circuit ground.
>
> http://wb9kzy.com/keyall.htm
>
> This allows for positive, negative, and even AC amplifier keying, all from
> one circuit.  A commercial version, already wired/assembled is shown on a
> web link and is manufactured by Gary, KD9SV.  There are other commercial amp
> keying interfaces available, but not all of them will accommodate
> high-voltage, negative key lines.
>
> If you operate much CW, I would go one step further and find an Ameritron
> QSK-5, designed by W8JI.  It's really an excellent design.  I use one
> (highly modified) between my K3 and SPE 1K-FA amp.  The mods take care of
> some additional design deficiencies within the SPE amp.
>
> Paul, W9AC
>
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