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KPA500problem - Half output power

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4z1tl

KPA500problem - Half output power

Hello Elecrafters

Thanks for your time on this, & I hope to find you all in good health

My setup is K3+KPA500+KAT500.

Sometime ago due to probably high SWR (water in the Pl259 leading to
KAT-500) the KPA-500 stopped after a loud noise (can't tell whether KPA or
KAT) was heard.

When I reset it & checked all bands into a dummy load (no tuner), It
delivered half the regular output power on all bands. (25w in for appx. 150w
out).

I don't know if this means 1 side of the PA is gone, or is there some 3db
pad connected permanently.

Any ideas for test procedures?

Also how safe (forbidden?) is it to operate the amp in this "half-power"
condition?

Thanks in advance,

Isaac, 4Z1TL

KPA SN 01090

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Bob McGraw - K4TAX

Re: KPA500problem - Half output power

I wouldn’t run the KPA500 at half power. And 25 watts of drive is certainly more than mine requires to attain rated power, except on 6M where it requires 25 watts.

As to power output indicators, I used my Bird43 and a 500 watt element with a known good 50 ohm load. I then calibrated the indications per the manual for my KPA500. That’s when I did the ALC calibration and setup for each band.

Sure works nice when everything is correct and correctly calibrated.

Bob, K4TAX

Sent from my iPhone

> On May 16, 2020, at 12:25 PM, TL_Netvision <[hidden email]> wrote:
>
>
>
> Hello Elecrafters
>
>
>
> Thanks for your time on this, & I hope to find you all in good health
>
>
>
> My setup is K3+KPA500+KAT500.
>
>
>
>
>
> Sometime ago due to probably high SWR (water in the Pl259 leading to
> KAT-500) the KPA-500 stopped after a loud noise (can't tell whether KPA or
> KAT) was heard.
>
> When I reset it & checked all bands into a dummy load (no tuner), It
> delivered half the regular output power on all bands. (25w in for appx. 150w
> out).
>
>
>
> I don't know if this means 1 side of the PA is gone, or is there some 3db
> pad connected permanently.
>
>
>
> Any ideas for test procedures?
>
> Also how safe (forbidden?) is it to operate the amp in this "half-power"
> condition?
>
>
>
>
>
> Thanks in advance,
>
>
>
> Isaac, 4Z1TL
>
> KPA SN 01090
>
>
>
> --
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
> ______________________________________________________________
> 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]
>

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

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Message delivered to [hidden email]

Elecraft mailing list

Re: KPA500problem - Half output power

Bob
I'm steering slightly off course and I feel I must come in: I presume that during the manufacturing process, the amplifier goes through a production process to set up the indicators using a lab quality load and modern, lab quality power meter, regularly calibrated. I have a Bird with various slugs and dummy load but I would not assume it was even close to the accuracy that Elecraft achieve even if I had just had it calibrated the day before. From memory the Bird is *only* 5% accurate on the day of calibration, whereas a modern lab quality digital power meter must surely be far better, perhaps in the 1% region. So, I'm questioning the need to change the factory settings. While on this topic, I'm curious to know how long the factory settings last and to what accuracy.

Apologies for the drift.

73 David G3UNA

> On 16 May 2020 at 18:45 Bob McGraw K4TAX <[hidden email]> wrote:
>
>
> I wouldn’t run the KPA500 at half power. And 25 watts of drive is certainly more than mine requires to attain rated power, except on 6M where it requires 25 watts.
>
> As to power output indicators, I used my Bird43 and a 500 watt element with a known good 50 ohm load. I then calibrated the indications per the manual for my KPA500. That’s when I did the ALC calibration and setup for each band.
>
> Sure works nice when everything is correct and correctly calibrated.
>
> Bob, K4TAX
>
>
> Sent from my iPhone
>
> > On May 16, 2020, at 12:25 PM, TL_Netvision <[hidden email]> wrote:
> >
> >
> >
> > Hello Elecrafters
> >
> >
> >
> > Thanks for your time on this, & I hope to find you all in good health
> >
> >
> >
> > My setup is K3+KPA500+KAT500.
> >
> >
> >
> >
> >
> > Sometime ago due to probably high SWR (water in the Pl259 leading to
> > KAT-500) the KPA-500 stopped after a loud noise (can't tell whether KPA or
> > KAT) was heard.
> >
> > When I reset it & checked all bands into a dummy load (no tuner), It
> > delivered half the regular output power on all bands. (25w in for appx. 150w
> > out).
> >
> >
> >
> > I don't know if this means 1 side of the PA is gone, or is there some 3db
> > pad connected permanently.
> >
> >
> >
> > Any ideas for test procedures?
> >
> > Also how safe (forbidden?) is it to operate the amp in this "half-power"
> > condition?
> >
> >
> >
> >
> >
> > Thanks in advance,
> >
> >
> >
> > Isaac, 4Z1TL
> >
> > KPA SN 01090
> >
> >
> >
> > --
> > This email has been checked for viruses by Avast antivirus software.
> > https://www.avast.com/antivirus
> > ______________________________________________________________
> > 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]
> >
>
>
> ______________________________________________________________
> 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]