[Elecraft] Shutdown on 50MHz CW

[Tom Childers, N5GE]

On Tue, 27 May 2008 09:19:41 +0100, Ian White GM3SEK <gm3sek at ifwtech.co.uk>
wrote:

>Hello Gary
>
>>    Based on the datasheets for the drivers and the finals, I suspect that
>>the problem is with the LPA (10W) drivers rather than the 100W PA. 
>>Y?all can help to prove or disprove my suspicion by testing to see if the
>>same thing happens below the crossover point where it 100 W PA kicks
>>in.  (I don?t recall exactly where that is & somewhere between 8 and 12
>>watts.)  Or better yet, you could temporarily disable the PA in firmware. 
>>In this way you might be able to push the drivers harder still.
>
>With the PA bypassed, the problem disappears. The PA temperature 
>indication still works, but it remains steady because the PA is 
>inactive.
>
>This is exactly what we should expect  - that is, <IF> the problem we're 
>all experiencing is due to RF affecting the PA temperature indication, 
>and then triggering some protective shutdown mechanism. (The LPA does 
>not send a temperature output to the CPU.)
>
>Other things that haven't helped:
>
>* Bypassing the PA temperature sensor (Q1). I wondered if this 
>diode-connected transistor might have been rectifying RF, but evidently 
>it isn't - the PA temp indication bounces around same as before.
>
>* Making a shorter ground connection between the top rear corner of the 
>KAT3 board and the nearby bolt for the ANT1 socket. Directly soldering 
>two solder tags together made no improvement.
>

*** IMPORTANT ***

>Probably the most relevant thing at this time is the message from Tom, 
>N5GE, that Elecraft are aware of it and are working on a firmware 
>solution. With the Es season already in full swing, it can't come soon 
>enough!

Although I am experiencing the power shutdown on 6m, the issue I reported to
Elecraft was not related to power shutdown.  It was related to using CW in the
SSB modes on all bands.  I just happened to find the trouble while on 6m during
last week's opening.

The anomaly I reported was that after using CW on SSB on any band and then
speaking into the microphone showed extreme flat topping on my monitor scope
(SM-230).  It was as if I hade turned the compression and mic gain up to
maximum.  Keeping the output power at 100w or below avoids this issue on my K3
(SN 806).  This is what Gary at Elecraft told me they knew about.

Tapping the ATU TUNE button puts things back in order.  Probably because the
tuner reduces the power to do the tuning and doing so may set everything back to
normal.

*** END ***

As for the 6m power shutdown issues, I'm sure that Elecraft is very aware of the
6m power problem after the 6m band openings we experienced here in North America
during the past week.

73,

Tom, N5GE - SWOT 3537 - Grid EM12jq

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