K3s/KPA500 communication issue?

[Mike Dodd]

Occasionally it seems my K3s doesn't know the STBY/OPER state of my
KPA500. I also have a KAT500 for my Carolina Windom.

Here's the first scenario: K3 in CW mode. I put the KPA in STBY and hit
TUNE on the KAT and on the K3. When the tune is complete, I send one
dash and note the 100W LED on the KPA. So far, so good.

Next I put the KPA in OPER mode. The K3 power level is already set to
about 10W, sufficient for about 250W on the KPA. Now I send a dash.

Occasionally the KPA power indicator shoots up to 700W, and the KPA
faults. When I clear the fault, the KPA is in STBY, and if I send a
dash, I see the 100W LED come on. if I then put the KPA in OPER and send
a dash, USUALLY I get the expected 250W output, but occasionally it
shoots up to 700W and faults again.

Now for the second scenario. With the KPA in OPER and outputting 250W, I
switch it to STBY, then send a dash. I expect to see the 100W LED, but
it does not light. If I look at the K3 RF bar graph, it shows 10W, not
100W. If I slightly turn the K3 PWR knob, it shows about 10W, not 100W.

Until recently, the K3 ALWAYS switched back to my normal setting of 100W
when the KPA is in STBY. The fact that it occasionally remains at 10W
seems to indicate that it doesn't know the KPA is in STBY.

Furthermore, the first scenario, where the KPA output shoots to 700W and
it faults, seems to indicate that the K3 is sending it 100 watts --
another indication that the K3 doesn't know the KPA is in OPER, and thus
doesn't reduce its output power to 10W.

Is there any way to diagnose this problem, and more importantly, to fix it?

Thanks for any and all guidance.

--
73, Mike N4CF
Louisa County, VA USA
Elecraft K3s / P3 / KPA500 / KAT500
Carolina Windom up 45'
http://n4cf.mdodd.com
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[Alan - G4GNX]

Mike, I'm not sure if this is relevant or not but I also have a tale of
woe, similar to yours.

My main antenna is also an OSCFD and not really cut for 80 metres, so
the SWR is always a bit higher than I prefer, possibly approaching 2:1.

My setup is a K3S + P3, KPA500 and KAT500.

A couple nights ago I was attempting to call a special event station in
a pileup on 80 metres and decided to turn the KPA500 on. I was only
running with around 11W from the K3S, giving me about 200W output from
the KPA500.
After 'shouting' a couple of times, the SWR was just below 2:1 but the
KPA500 didn't like it and suddenly faulted. When I tried to TX barefoot
from the K3S, there was no output - nothing showing on the K3S display.
I checked the power setting and it was 100W. I had previously power
cycled the KPA500 and it was in Standby. The only way I could get the
K3S to TX was to power cycle it, then all was back to normal.

I ran the KPA500 in Operate again for a few moments to check that it was
OK and all seemed normal, but I didn't pursue it on 80m because I didn't
want to push my luck. :-)

A couple days later on a regular 40 metre net, I ran the KPA500 again
for over an hour (on SSB) and have had no issues.

I've not checked the manuals as to whether the original action is a
safety feature or a bug.

73,

Alan. G4GNX


------ Original Message ------
From: "Mike Dodd" <[hidden email]>
To: [hidden email]
Sent: 14/11/2020 01:59:57
Subject: [Elecraft] K3s/KPA500 communication issue?

>Occasionally it seems my K3s doesn't know the STBY/OPER state of my KPA500. I also have a KAT500 for my Carolina Windom.
>
>Here's the first scenario: K3 in CW mode. I put the KPA in STBY and hit TUNE on the KAT and on the K3. When the tune is complete, I send one dash and note the 100W LED on the KPA. So far, so good.
>
>Next I put the KPA in OPER mode. The K3 power level is already set to about 10W, sufficient for about 250W on the KPA. Now I send a dash.
>
>Occasionally the KPA power indicator shoots up to 700W, and the KPA faults. When I clear the fault, the KPA is in STBY, and if I send a dash, I see the 100W LED come on. if I then put the KPA in OPER and send a dash, USUALLY I get the expected 250W output, but occasionally it shoots up to 700W and faults again.
>
>Now for the second scenario. With the KPA in OPER and outputting 250W, I switch it to STBY, then send a dash. I expect to see the 100W LED, but it does not light. If I look at the K3 RF bar graph, it shows 10W, not 100W. If I slightly turn the K3 PWR knob, it shows about 10W, not 100W.
>
>Until recently, the K3 ALWAYS switched back to my normal setting of 100W when the KPA is in STBY. The fact that it occasionally remains at 10W seems to indicate that it doesn't know the KPA is in STBY.
>
>Furthermore, the first scenario, where the KPA output shoots to 700W and it faults, seems to indicate that the K3 is sending it 100 watts -- another indication that the K3 doesn't know the KPA is in OPER, and thus doesn't reduce its output power to 10W.
>
>Is there any way to diagnose this problem, and more importantly, to fix it?
>
>Thanks for any and all guidance.
>
>-- 73, Mike N4CF
>Louisa County, VA USA
>Elecraft K3s / P3 / KPA500 / KAT500
>Carolina Windom up 45'
>http://n4cf.mdodd.com
>______________________________________________________________
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>
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>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to [hidden email]

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[Tim Seed]

Use the kpa utility and check the fault codes.

In my case (prefix du3) it has always been due to input power variance. And as you describe, the following day - everything has been fine.

Tim
   Du3tw

Sent from my iPhone

> On 14/11/2020, at 23:12, Alan - G4GNX <[hidden email]> wrote:
>
> Mike, I'm not sure if this is relevant or not but I also have a tale of woe, similar to yours.
>
> My main antenna is also an OSCFD and not really cut for 80 metres, so the SWR is always a bit higher than I prefer, possibly approaching 2:1.
>
> My setup is a K3S + P3, KPA500 and KAT500.
>
> A couple nights ago I was attempting to call a special event station in a pileup on 80 metres and decided to turn the KPA500 on. I was only running with around 11W from the K3S, giving me about 200W output from the KPA500.
> After 'shouting' a couple of times, the SWR was just below 2:1 but the KPA500 didn't like it and suddenly faulted. When I tried to TX barefoot from the K3S, there was no output - nothing showing on the K3S display. I checked the power setting and it was 100W. I had previously power cycled the KPA500 and it was in Standby. The only way I could get the K3S to TX was to power cycle it, then all was back to normal.
>
> I ran the KPA500 in Operate again for a few moments to check that it was OK and all seemed normal, but I didn't pursue it on 80m because I didn't want to push my luck. :-)
>
> A couple days later on a regular 40 metre net, I ran the KPA500 again for over an hour (on SSB) and have had no issues.
>
> I've not checked the manuals as to whether the original action is a safety feature or a bug.
>
> 73,
>
> Alan. G4GNX
>
>
> ------ Original Message ------
> From: "Mike Dodd" <[hidden email]>
> To: [hidden email]
> Sent: 14/11/2020 01:59:57
> Subject: [Elecraft] K3s/KPA500 communication issue?
>
>> Occasionally it seems my K3s doesn't know the STBY/OPER state of my KPA500. I also have a KAT500 for my Carolina Windom.
>>
>> Here's the first scenario: K3 in CW mode. I put the KPA in STBY and hit TUNE on the KAT and on the K3. When the tune is complete, I send one dash and note the 100W LED on the KPA. So far, so good.
>>
>> Next I put the KPA in OPER mode. The K3 power level is already set to about 10W, sufficient for about 250W on the KPA. Now I send a dash.
>>
>> Occasionally the KPA power indicator shoots up to 700W, and the KPA faults. When I clear the fault, the KPA is in STBY, and if I send a dash, I see the 100W LED come on. if I then put the KPA in OPER and send a dash, USUALLY I get the expected 250W output, but occasionally it shoots up to 700W and faults again.
>>
>> Now for the second scenario. With the KPA in OPER and outputting 250W, I switch it to STBY, then send a dash. I expect to see the 100W LED, but it does not light. If I look at the K3 RF bar graph, it shows 10W, not 100W. If I slightly turn the K3 PWR knob, it shows about 10W, not 100W.
>>
>> Until recently, the K3 ALWAYS switched back to my normal setting of 100W when the KPA is in STBY. The fact that it occasionally remains at 10W seems to indicate that it doesn't know the KPA is in STBY.
>>
>> Furthermore, the first scenario, where the KPA output shoots to 700W and it faults, seems to indicate that the K3 is sending it 100 watts -- another indication that the K3 doesn't know the KPA is in OPER, and thus doesn't reduce its output power to 10W.
>>
>> Is there any way to diagnose this problem, and more importantly, to fix it?
>>
>> Thanks for any and all guidance.
>>
>> -- 73, Mike N4CF
>> Louisa County, VA USA
>> Elecraft K3s / P3 / KPA500 / KAT500
>> Carolina Windom up 45'
>> http://n4cf.mdodd.com
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>
> ______________________________________________________________
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[Elecraft mailing list]

This question has come up several times over the years, and I have always followed the threads closely, since I have occasionally had the same issue.

The consensus seems to indeed involve a communication issue: the KPA500 sends a signal to the K3 when its operational status changes, but for whatever reason the K3 fails to see message. There is no expectation that the K3 will “ACK” the signal from the KPA500.

I have found it important to watch the K3 LCD to see that the operational change has actually been received and acted upon. If not, cycling the OPER switch on the KPA500 until you actually see the K3 is in the desired mode.

Works every time…

Tom W4KX

From: [hidden email]
Sent: Sunday, November 15, 2020 5:47 AM
To: Elecraft Reflector
Subject: Re: [Elecraft] K3s/KPA500 communication issue?

U

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[Mike Dodd]

Thanks to all who offered suggestions. Let me touch on some:

* CONFIG:PWR SET is PEr bAnd - Was and is.

* Reload firmware - Done; no change.

* TX GAIN CAL on the K3 - Not yet; will look into this.

* Plug/replug cables - On the to-do list.

* Other software sending commands - The problem has occurred when no
other software is running.

* Ks LCD confirms KPA STBY/OPER change - Yes, but often the K3 PWR is
set to 10W-12W after the KPA switches to STBY, which is the normal drive
power to the KPA. I.e., if I hit send a dash, I get 10W output to the
antenna.

* KPA fault log - Indicates high SWR.

My antenna has had some issues recently, and I am still working on that,
so the KPA fault log is definitely relevant. I have connected my dummy
load to the PL-259 that connects to the antenna's balun, and sent 500W
to it. No SWR problems, but I will do this again before digging into the
balun.

So there are some things I still need to check. But first I want to try
getting the antenna working right.

Thanks gain.

73, Mike N4CF

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