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K3S/100 very low TX power

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gm3sek

K3S/100 very low TX power

My K3S/100 has gone into an unusual state where the maximum power
available - on any mode, any band - is about 1.5-2W. This is independent
of any PWR setting above 1W, and the PA does not engage at higher PWR
settings.

All this began on Friday afternoon when I switched on the rig. The K3S
had been working normally a few weeks ago, but hadn't been used for
transmitting in the meantime.

An external power meter confirmed that the TX could not deliver more
than about 1.5-2W. This was confirmed again by the failure messages
from a TX power calibration. While troubleshooting, I progressively
uninstalled the KPA3 followed by the KPAIO3A adapter board, but with no
change. Even in the simplest 10W configuration with only the small
bridge board in place between the two PA connectors, the K3S would still
only deliver 1.5-2W with no effective PWR control.

I also tried most of the other common tests: unplugged everything else;
reloaded an older saved configuration; EEINIT; reloaded the saved
configuration again. No change.

But I also noticed that the firmware was one release behind the times,
so for lack of any other ideas I did a complete firmware upgrade to the
latest MCU 5.35 / DSP 2.86 / FPF 1.24 - and it started working again!
Normal power output up to 10W, and fully variable up to 100W after
reinstalling the PA module. Another TX calibration confirmed that
everything was fine.

That pleasant surprise seemed to indicate that the problem had been more
related to firmware than to hardware.

By Friday evening, I believed the problem had gone away... but I should
have known better.

Today it has failed again, exactly the same way as before. Reloading the
same latest firmware didn't work a second time.

So now it's the weekend and I'm all out of ideas.

While I wait until Monday to contact Elecraft Support, could anyone in
the group offer any suggestions, please?

73 from Ian GM3SEK

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wayne burdick

Re: K3S/100 very low TX power

Administrator

Ian,

This sounds like an intermittent connection somewhere, possibly in the 10-W amplifier stage.

Try re-tightening all of the hardware on the bottom covers, including the screws that hold the PA device tabs to bottom cover B. Also try reseating the 10-W amp module.

If this doesn't help, try measuring the 0-dBm drive at the XVTR OUT jack. For this purpose you need to put CONFIG:KXV3B into TEST mode.

If you get a full 0 to 1.5 dBm output at XVTR OUT (into a 50-ohm load), but low power output from the 10-W amp module, then the latter is probably implicated. Look at both sides of the module very carefully to see if a component is not soldered at one end, etc. This is rare but it can happen.

Also look at the components on the RF board just behind the 10-W amp module.

I can give you more detailed signal tracing info if needed.

Wayne
N6KR

On Sep 12, 2015, at 1:57 PM, "Ian White" <[hidden email]> wrote:

> My K3S/100 has gone into an unusual state where the maximum power
> available - on any mode, any band - is about 1.5-2W. This is independent
> of any PWR setting above 1W, and the PA does not engage at higher PWR
> settings.
>
> All this began on Friday afternoon when I switched on the rig. The K3S
> had been working normally a few weeks ago, but hadn't been used for
> transmitting in the meantime.
>
> An external power meter confirmed that the TX could not deliver more
> than about 1.5-2W. This was confirmed again by the failure messages
> from a TX power calibration. While troubleshooting, I progressively
> uninstalled the KPA3 followed by the KPAIO3A adapter board, but with no
> change. Even in the simplest 10W configuration with only the small
> bridge board in place between the two PA connectors, the K3S would still
> only deliver 1.5-2W with no effective PWR control.
>
> I also tried most of the other common tests: unplugged everything else;
> reloaded an older saved configuration; EEINIT; reloaded the saved
> configuration again. No change.
>
> But I also noticed that the firmware was one release behind the times,
> so for lack of any other ideas I did a complete firmware upgrade to the
> latest MCU 5.35 / DSP 2.86 / FPF 1.24 - and it started working again!
> Normal power output up to 10W, and fully variable up to 100W after
> reinstalling the PA module. Another TX calibration confirmed that
> everything was fine.
>
> That pleasant surprise seemed to indicate that the problem had been more
> related to firmware than to hardware.
>
> By Friday evening, I believed the problem had gone away... but I should
> have known better.
>
> Today it has failed again, exactly the same way as before. Reloading the
> same latest firmware didn't work a second time.
>
> So now it's the weekend and I'm all out of ideas.
>
> While I wait until Monday to contact Elecraft Support, could anyone in
> the group offer any suggestions, please?
>
>
> 73 from Ian GM3SEK
>
>
>
> ______________________________________________________________
> 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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gm3sek

Re: K3S/100 very low TX power

Thanks for the very prompt response, Wayne!

[Continued off-list.]

73 from Ian GM3SEK

>-----Original Message-----
>From: Elecraft [mailto:[hidden email]] On Behalf Of
>Wayne Burdick
>Sent: 12 September 2015 22:12
>To: Ian White
>Cc: 'Elecraft Reflector'
>Subject: Re: [Elecraft] K3S/100 very low TX power
>
>Ian,
>
>This sounds like an intermittent connection somewhere, possibly in the

10-
>W amplifier stage.
>
>Try re-tightening all of the hardware on the bottom covers, including
the
>screws that hold the PA device tabs to bottom cover B. Also try
reseating
>the 10-W amp module.
>
>If this doesn't help, try measuring the 0-dBm drive at the XVTR OUT
jack.
>For this purpose you need to put CONFIG:KXV3B into TEST mode.
>
>If you get a full 0 to 1.5 dBm output at XVTR OUT (into a 50-ohm load),
but
>low power output from the 10-W amp module, then the latter is probably
>implicated. Look at both sides of the module very carefully to see if a
>component is not soldered at one end, etc. This is rare but it can
happen.

>
>Also look at the components on the RF board just behind the 10-W amp
>module.
>
>I can give you more detailed signal tracing info if needed.
>
>Wayne
>N6KR
>
>
>
>On Sep 12, 2015, at 1:57 PM, "Ian White" <[hidden email]> wrote:
>
>> My K3S/100 has gone into an unusual state where the maximum power
>> available - on any mode, any band - is about 1.5-2W. This is

independent
>> of any PWR setting above 1W, and the PA does not engage at higher PWR
>> settings.
>>
>> All this began on Friday afternoon when I switched on the rig. The
K3S
>> had been working normally a few weeks ago, but hadn't been used for
>> transmitting in the meantime.
>>
>> An external power meter confirmed that the TX could not deliver more
>> than about 1.5-2W. This was confirmed again by the failure messages
>> from a TX power calibration. While troubleshooting, I progressively
>> uninstalled the KPA3 followed by the KPAIO3A adapter board, but with
no
>> change. Even in the simplest 10W configuration with only the small
>> bridge board in place between the two PA connectors, the K3S would
still
>> only deliver 1.5-2W with no effective PWR control.
>>
>> I also tried most of the other common tests: unplugged everything
else;
>> reloaded an older saved configuration; EEINIT; reloaded the saved
>> configuration again. No change.
>>
>> But I also noticed that the firmware was one release behind the
times,
>> so for lack of any other ideas I did a complete firmware upgrade to
the

>> latest MCU 5.35 / DSP 2.86 / FPF 1.24 - and it started working again!
>> Normal power output up to 10W, and fully variable up to 100W after
>> reinstalling the PA module. Another TX calibration confirmed that
>> everything was fine.
>>
>> That pleasant surprise seemed to indicate that the problem had been
>more
>> related to firmware than to hardware.
>>
>> By Friday evening, I believed the problem had gone away... but I

should
>> have known better.
>>
>> Today it has failed again, exactly the same way as before. Reloading
the
>> same latest firmware didn't work a second time.
>>
>> So now it's the weekend and I'm all out of ideas.
>>
>> While I wait until Monday to contact Elecraft Support, could anyone
in

>> the group offer any suggestions, please?
>>
>>
>> 73 from Ian GM3SEK
>>
>>
>>
>>
>______________________________________________________________
>> 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]