[Elecraft] K3S/100 very low TX power

[Ian White]

Thanks for the very prompt response, Wayne!

[Continued off-list.]

73 from Ian GM3SEK


>-----Original Message-----
>From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] 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" <gm3sek at ifwtech.co.uk> 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:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to n6kr at elecraft.com
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:Elecraft at mailman.qth.net
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to gm3sek at ifwtech.co.uk