odd happening with KPA500

[Tony Estep]

My K3 and KPA500 have lived happily for months, ever since their first
blissful night together. But today something bizarre happened, and I'm
just wondering if anyone else has seen this:

I had a couple of QSOs on 15 meters, with everything working FB as it
always does. But then a little later when I tried to call a DX station
on CW, the amp faulted, claiming PWRIN HI. I reset it, verified that
the power in was 30W, and tapped the key. Same result.

Then (here's the bizarre part) I reset it, pressed TUNE, and advanced
the power from its normal tune level of 8W up to 30W; the amp put out
500W, no problem. Then I set the K3's transmit output power to 3W and
tapped the key; PWRIN HI fault.

So in other words it tolerated 30W of drive if I applied it via the
TUNE button, but not even 3W of drive in normal transmit.

I checked the antenna, the grounding connections, and everything else;
nothing had changed from the configuration that has been working
perfectly on all bands for months. Then I tried the amp on all other
bands, 80 thru 10. All operations perfectly normal.

Finally I powered off the amp and switched the rear 0/1 switch off,
and fired it up again. 15 meters returned to normal, and all is well.

My guess is that that the PIC chip is addressing some volatile memory
where intermediate values are stored, and a memory location pertinent
to 15 meters only got scrambled by something. But that's just a guess;
actually, I dunno what happened, but I sure hope it doesn't happen any
more. Anybody have any thoughts?

Tony KT0NY


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[Iain MacDonnell - N6ML-2]

Tony,

Have you tried running through the TX gain calibration on the K3? It
may be overshooting on key-down....

    ~iain / N6ML


On Mon, Feb 6, 2012 at 4:39 PM, Tony Estep <[hidden email]> wrote:

> My K3 and KPA500 have lived happily for months, ever since their first
> blissful night together. But today something bizarre happened, and I'm
> just wondering if anyone else has seen this:
>
> I had a couple of QSOs on 15 meters, with everything working FB as it
> always does. But then a little later when I tried to call a DX station
> on CW, the amp faulted, claiming PWRIN HI. I reset it, verified that
> the power in was 30W, and tapped the key. Same result.
>
> Then (here's the bizarre part) I reset it, pressed TUNE, and advanced
> the power from its normal tune level of 8W up to 30W; the amp put out
> 500W, no problem. Then I set the K3's transmit output power to 3W and
> tapped the key; PWRIN HI fault.
>
> So in other words it tolerated 30W of drive if I applied it via the
> TUNE button, but not even 3W of drive in normal transmit.
>
> I checked the antenna, the grounding connections, and everything else;
> nothing had changed from the configuration that has been working
> perfectly on all bands for months. Then I tried the amp on all other
> bands, 80 thru 10. All operations perfectly normal.
>
> Finally I powered off the amp and switched the rear 0/1 switch off,
> and fired it up again. 15 meters returned to normal, and all is well.
>
> My guess is that that the PIC chip is addressing some volatile memory
> where intermediate values are stored, and a memory location pertinent
> to 15 meters only got scrambled by something. But that's just a guess;
> actually, I dunno what happened, but I sure hope it doesn't happen any
> more. Anybody have any thoughts?
>
> Tony KT0NY
>
>
> --
> http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html

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[Tony Estep]

On Mon, Feb 6, 2012 at 6:49 PM, iain macdonnell - N6ML <[hidden email]> wrote:
> Have you tried running through the TX gain calibration...
===========
Well, as noted, it worked before, it works now, and it wasn't working
when the K3 was set to output 3 watts. Moreover, I changed nothing in
the K3, just re-booted the KPA500. All of that seems inconsistent with
a power overshoot from the K3.

Tony KT0NY





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[Iain MacDonnell - N6ML-2]

On Mon, Feb 6, 2012 at 4:53 PM, Tony Estep <[hidden email]> wrote:
> On Mon, Feb 6, 2012 at 6:49 PM, iain macdonnell - N6ML <[hidden email]> wrote:
>> Have you tried running through the TX gain calibration...
> ===========
> Well, as noted, it worked before, it works now, and it wasn't working
> when the K3 was set to output 3 watts. Moreover, I changed nothing in
> the K3, just re-booted the KPA500. All of that seems inconsistent with
> a power overshoot from the K3.

Not sure I followed the sequence of events right. If it's really
faulting with 3W of drive, something is very wrong!

One thing that has caught me out (momentarily) in situations like this
.... if the amp faults, and you reach for the K3's PWR control, you'll
be adjusting the *standby* PWR. You have to clear the fault and put
the amp back in Operate before adjusting the drive power. You probably
did, but just in case..... ;)

    ~iain / N6ML
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