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KPA1500 not amplifying

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KPA1500 not amplifying

I used my K3S driving my KPA1500 on Saturday during Makrothen and state QSO parties with no issues. I have the integration cable and RG-8X for the RF path.

Sunday AM with the K3S set to 22 W, the KPA1500 was outputting 22 W more or less, not the 750 W I expected and got the day before.

With the K3S set to 11.5 W, the KPA1500 produced about 400 W out.

With the K3S set at 100 W, and the KPA1500 in STBY, the KPA1500 power meter read 100 W more or less.

Later in the day the situation self-healed, but the healing did not last.

Trouble shooting ideas ? The recent KPA1500 manual troubleshooting section suggests the obvious stuff which is irrelevant.

N7WY - Bob R
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Eric Swartz - WA6HHQ

Re: KPA1500 not amplifying

Administrator

Hi Bob - I just saw your post below.

Please contact [hidden email] immediately and we'll help you figure out
what is happening. Using the KPA1500 utility to download and sending us your
KPA1500 config file is always required in cases like this and it will also help
us quickly diagnose what's up. (that file contains the full amp setup and fault
log history.) Hopefully, this may just be a cockpit error.

Also, NEVER drive the KPA1500 at 100W! That is well in excess of its fault level
and can damage the amp. Our normal max input drive level is about 61 W or so if
I recall correctly. Above that point the 1500 automatically lights the yellow
OVR light and switches on a -3 dB input attenuator. After continuous slight
drive for 10-20 secs at above this max drive level the amp will then hard fault
into standby. Never increase drive when the OVR light is on - that will only
increase the risk of damaging the amp.

OVR and the 3 dB attenuator will activate for overdrive, high reflected power,
high PA current etc. When it lights, that is a message to reduce drive and
correct the problem. Once the drive is reduced, after several seconds the OVR
light and input attenuator will turn back off.

73,

Eric
/elecraft.com/

On 10/17/2018 7:45 AM, Bob Rennard via Elecraft wrote:

> I used my K3S driving my KPA1500 on Saturday during Makrothen and state QSO parties with no issues. I have the integration cable and RG-8X for the RF path.
>
>
> Sunday AM with the K3S set to 22 W, the KPA1500 was outputting 22 W more or less, not the 750 W I expected and got the day before.
>
> With the K3S set to 11.5 W, the KPA1500 produced about 400 W out.
>
> With the K3S set at 100 W, and the KPA1500 in STBY, the KPA1500 power meter read 100 W more or less.
>
>
> Later in the day the situation self-healed, but the healing did not last.
>
>
> Trouble shooting ideas ? The recent KPA1500 manual troubleshooting section suggests the obvious stuff which is irrelevant.
>
>
> N7WY - Bob R
> ______________________________________________________________
> 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

Re: KPA1500 not amplifying

In reply to this post by Elecraft mailing list

Turns out, it is not the KPA1500 not amplifying, but rather the KPA3A final amplifier stage in my K3S is acting like it has tubes, not FETs. It has to warm up at 30 watts out, and then the power can be reduced to 20 watts. Weirdly, changing the power level above 20 watts seems to reset tbe behavior so it has to be warmed again. The KPA3A module that is present is the 2nd replacement/exchange. The first 2 had high 2 tone IMD issues on SSB.
My trustworthy K3 is now driving tbe KPA1500 without issues.
Thanks for all the off reflector counsel and 73,
Bob R n7wy

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Eric Swartz - WA6HHQ

Re: KPA1500 not amplifying

Administrator

In reply to this post by Elecraft mailing list

Hi Bob - Have you run the K3 TX gain calibration on each band into a dummy load
(or very low SWR Ant.) ? If that is out of cal, it could easily create
symptoms like this.

73,
Eric
/elecraft.com/

On 10/22/2018 2:02 PM, n7wy via Elecraft wrote:
> Turns out, it is not the KPA1500 not amplifying, but rather the KPA3A final amplifier stage in my K3S is acting like it has tubes, not FETs. It has to warm up at 30 watts out, and then the power can be reduced to 20 watts. Weirdly, changing the power level above 20 watts seems to reset tbe behavior so it has to be warmed again. The KPA3A module that is present is the 2nd replacement/exchange. The first 2 had high 2 tone IMD issues on SSB.
> My trustworthy K3 is now driving tbe KPA1500 without issues.
> Thanks for all the off reflector counsel and 73,
> Bob R n7wy
>

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Elecraft mailing list

Re: KPA1500 not amplifying

Eric et al -

I performed the wattmeter calibration from page 52 of the user manual,
and then did the 5 and 50 watt TX gain calibration using the K3(s) Utility.

I notice that during the first transmission of AFSK RTTY into a Palstar
dummy load, the KPA1500 output power grows to the desired output level
in a few seconds, but in subsequent transmissions, the power level
immediately reaches the desired level. Unfortunately, I did not have the
LP-100 between the K3s and the amp.

I've been using the KPA1500 with my K3 using KEY line instead of the
KPAK cable, but not on RTTY and do not see this ramp up.

73,

Bob R - KPA1500 #67

On 2018-10-24 19:44, Eric Swartz - WA6HHQ, Elecraft wrote:

> Hi Bob - Have you run the K3 TX gain calibration on each band into a
> dummy load (or very low SWR Ant.) ? If that is out of cal, it could
> easily create symptoms like this.
>
> 73,
> Eric
> /elecraft.com/
>
> On 10/22/2018 2:02 PM, n7wy via Elecraft wrote:
>> Turns out, it is not the KPA1500 not amplifying, but rather the KPA3A final amplifier stage in my K3S is acting like it has tubes, not FETs. It has to warm up at 30 watts out, and then the power can be reduced to 20 watts. Weirdly, changing the power level above 20 watts seems to reset tbe behavior so it has to be warmed again. The KPA3A module that is present is the 2nd replacement/exchange. The first 2 had high 2 tone IMD issues on SSB.
>> My trustworthy K3 is now driving tbe KPA1500 without issues.
>> Thanks for all the off reflector counsel and 73,
>> Bob R n7wy
>>
>

Don Wilhelm

Re: KPA1500 not amplifying

Bob,

That power ramp up is often caused by not driving the K3 with sufficient
audio.
Your audio level should be adjusted to produce 4 bars solid on the K3
ALC meter with the 5th bar flashing.

I have an article on my website www.w3fpr.com explaining the audio settings.

73,
Don W3FPR

On 11/9/2018 8:32 AM, Robert Rennard via Elecraft wrote:

> Eric et al -
>
> I performed the wattmeter calibration from page 52 of the user manual,
> and then did the 5 and 50 watt TX gain calibration using the K3(s) Utility.
>
> I notice that during the first transmission of AFSK RTTY into a Palstar
> dummy load, the KPA1500 output power grows to the desired output level
> in a few seconds, but in subsequent transmissions, the power level
> immediately reaches the desired level. Unfortunately, I did not have the
> LP-100 between the K3s and the amp.
>
> I've been using the KPA1500 with my K3 using KEY line instead of the
> KPAK cable, but not on RTTY and do not see this ramp up.
>