queer behaviour !

[Jacques Gaudron]

Hello
A good friend of mine, F6CVM, has a K3 as well as an Icom transceiver. He
uses an old Heath SB 230 as an amplifier.
When he connects Icom/SB 230, no problem.
But if he connects K3/SB 230, as soon as he plugs the cinch into the K3 key
out output , (with no drive), the  amplifier sets on the transmit position !
Did anyone meet the same problem or has a clue about it ?
Thanks for any idea...
Best 73 to all
Jacques de F9OJ

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[W8JI]

The SB230, like the SB200 and a few other amplifiers, has negative high
voltage keying line voltage. The voltage is well over 100 volts negative. It
is not compatible with the K3 and many other radios  that are designed for
the standard positive voltage lines.

It can actually damage many radios if the relay line of amplifiers like that
are plugged directly into radios. It is even bad for radios that have relays
to key amplifiers, because over time it can damage relay contacts even.

I would use some type of solid state relay isolation device.

> A good friend of mine, F6CVM, has a K3 as well as an Icom transceiver. He
> uses an old Heath SB 230 as an amplifier.
> When he connects Icom/SB 230, no problem.
> But if he connects K3/SB 230, as soon as he plugs the cinch into the K3
> key
> out output , (with no drive), the  amplifier sets on the transmit position
> !

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[P.B. Christensen]

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

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Guy, 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 <[hidden email]> 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
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[P.B. Christensen]

True, Guy.  Looking at the internal structure of the switching HEXFET used
in the K3, a protecting Zener diode appears between the source and drain
leads.  With a negative keying voltage, the Zener is actually forward biased
like a typical silicon switching diode.  So, the negative switching voltage
by itself is probably not the concern, but rather the resulting current
through the forward-biased Zener diode when a negative voltage is applied.
That diode probably only handles a fraction of the normal HEXFET switching
current, so all bets are off when using vintage amps that use a negative key
line.

Darn, with the addition of another series HEXFET, a cut of jumper W30, and a
return from the added HEXFET drain to the outer shell of the KEY OUT jack,
the K3 could safely switch both key line polarities.

Paul, W9AC


----- Original Message -----
From: "Guy Olinger K2AV" <[hidden email]>
To: "Paul Christensen" <[hidden email]>
Cc: "Elecraft" <[hidden email]>
Sent: Wednesday, August 18, 2010 9:18 AM
Subject: Re: [Elecraft] queer behaviour !


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.

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Nidge_(G0NIG)]

I'm going through the process of rebuilding a Heathkit SB-200.

One of the additions is a Softkey CCT from Harbach which will
reduce the -120Volt + to a value suitable for nearly all modern
tranceivers' PTT out line.  The cost of the CCT is about $27 and
easy to construct and install.

Regards

Nidge (G0NIG)

IO93dv
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html