[Elecraft] Powering on/off a KPA500. Was: Re: Elecraft Digest, Vol 266, Issue 17

[Bob Wilson, N6TV]

No PC software is needed.  A K3, K4 or K4/0 macro can easily power a KPA500
or KP1500 ON and OFF via AUX connectors, once you replace the Elecraft AUX
cables with something better.  The technique was first explained on page 21
of the K3 Remote Owner's Manual
<https://ftp.elecraft.com/K3-Remote/Manuals%20Downloads/K3%20Remote%20Owner's%20Manual%20%20Rev%20D.pdf>,
and was implemented in the Y-BOX v2.1 and later, so you don't need to
modify any cables.  Note that the macro documented in the K3 Remote manual
has a major typo -- it omits the trailing semicolon.  That semicolon is
*mandatory*, and it could cause the behavior that Jim and Joe are seeing.

K0XU has one of my Y-BOXs that was prewired to connect K3 AUX Pin 11 to
KPA500 AUX1 Pin 8 via straight Amphenol® 15-pin cables (unmodified Elecraft
AUX cables will NOT work if they are anywhere in the chain from K3 to
KAT500 to KPA500).  A block diagram was supplied with the Y-BOX explaining
how to code the macro and how to connect all the cables.

It's also explained here:
https://www.kkn.net/~n6tv/Y-BOX/Features.html#Remote

The following K3 macro will pulse CONFIG:DIGOUT1 ON and OFF (which pulses
KPA500 or KPA1500 AUX Pin 8 low).  This should toggle the KPA500 ON or OFF
(assuming the rear POWER switch is in the ON position):

MN019;MP001;MN255;MN019;MP000;MN255;

You may need to add a 200 ms delay in the middle of the string, like this,
to pulse Pin 8 to ground for 200 ms, but that is usually not required.

MN019;MP001;MN255;DE20;MN019;MP000;MN255;

Make sure you haven't coded any "Ohs" instead of "Zeroe" in your macro.
Make sure not to omit the last semicolon.  Make sure *CONFIG:DIGOUT1* is
*OFF* on all bands before running the macro.

On a K4, the macro commands to pulse K4 *MENU:DIGOUT1* ON and OFF for 200
ms are more straightforward (the K3 MN commands do not work on a K4).

DO1;DE020;DO0;

Again, none of this will work with standard Elecraft AUX cables anywhere in
the chain, because Elecraft AUX cables do not have anything wired to Pin 8
(PWR ON).  And you must not use straight DE-15 M/F cables between rig and
amp either, unless you have a Y-BOX in series with them to open the proper
pins (1, 4, 6, 7, and 8).

K3 or K4 AUX -> Y-BOX v2.1+ "RADIO" via straight DE-15 M/M
Y-BOX AMP AUX -> KAT500 XCVR -> via straight DE-15 M/F
KAT500 AMP -> KPA500 AUX1 via straight DE-15 M/F

For a KPA1500, omit the KAT500 from the chain:

K3 or K4 AUX -> Y-BOX v2.1+ "RADIO" via straight DE-15 M/M
Y-BOX AMP AUX -> KPA1500 AUX via straight DE-15 M/F

73,
Bob, N6TV
https://bit.ly/Y-BOX

On Sat, Jun 27, 2026 at 11:00 AM Jack Brindle via Elecraft <
elecraft at mailman.qth.net> wrote:

> Please tell us ho you have the K3, KPA500 and KAT500 connected. I have to
> assume there is a computer in the mix. The K3 cannot talk to the KPA500 to
> tell is to shut off, nor can it cause the KPA500 to power up. The same is
> true for the KAT500, although the KAT can power up on its own when power is
> applied. A computer or other “intelligent” device is needed to tell the KPA
> and KAT to power up. In the case of the KPA500, there are two ways to
> remotely power it up - one is to momentarily ground the power line in the
> AUX IO connector. This signal cannot be tied to the K3’s power signal
> because of differences in voltage levels. Connecting them will probably be
> a good reason to send the KPA back for repairs. The second method is to
> send a “P” (just the P, no quotes needed) to the KPA500 when it is off
> (using the serial port). After it powers up, you can shut it off by sending
> the “^ON;” command to the KPA500. See the KAT500 serial command reference
> for info on commands specific to it.
>
> And again, the K3 does not send data to the KPA500. The Auxbus is strictly
> send-only from the KPA500. The only signals that go from the K3 to the KPA
> are the band signals and PTT.
>
> Note that the KPA1500 and KPA500 communicate differently - I don’t have an
> answer for Jim on his situation.
>
> Second, please trim your list emails when replying to digests, and follow
> the request to change the subject line. It cuts down on the amount of stuff
> we have to look through, and tells us which of the message you are replying
> to.
>
> 73,
> Jack W6FB
>
> > On Jun 27, 2026, at 12:00 PM, Joseph Koester via Elecraft <
> elecraft at mailman.qth.net> wrote:
> >
> > I have a similar issue with my K3 and my KPA500. I cannot turn the amp
> off.
> > I can turn the tuner off but not the amplifier.
> >
> > Joe/W4NSA
> >
> > On Sat, Jun 27, 2026, 11:01 <elecraft-request at mailman.qth.net> wrote:
> >
> >>
> >> Message: 1
> >> Date: Sat, 27 Jun 2026 00:17:07 -0500
> >> From: Jim Rhodes <jimk0xu at gmail.com>
> >> To: elecraft at mailman.qth.net
> >> Subject: [Elecraft] K4/KPA500 macro question
> >> Message-ID:
> >>        <CALhxr4ZyaBLACkEM_3O-1iwJyWgW+wgJWKEWWpQDrFbZMQLz=
> >> w at mail.gmail.com>
> >> Content-Type: text/plain; charset="UTF-8"
> >>
> >> I am trying to set up macros to turn the KPA500 on and off.  I seem to
> have
> >> them entered correctly in the K4D and in the KPA500 app.  But the app
> will
> >> turn the amp on but not off.  The K4 will turn it off but not on.
> Object
> >> is to get it set up for use with the K4/0.  Does anyone how I messed
> those
> >> up?
> >>
> >> Jim K0XU
> >> jim at rhodesend.net