[Elecraft] K2/KPA100 40M SSB ALC Problem?

[J-F VA2SS]

Thanks to Don Wilhem again ,and again !!! Youuhou !!

I got this behavior when testing my DATA port on my K2 trying PSK31 and
Pactor-2. The power output on 40m and 20m was way off between the two bands
using the digital mode. BUT, with this mod, it solved all my problems !!!

First of all, I think this mod should apply to all of you doing or not
digital mode with their K2.

AND...... I really hope I will meet Don Wilhem face to face one time in my
life to shake hands and telling him.... « Don, really thanks to you for all
your contributions to this discussion group !!!! »

BTW, I will be at Dayton this year, just in case... my first time. :-)

73

J-F VA2SS (formerly VA2VYZ)



Don Wilhelm wrote:
> 
> The conditions you describe are almost identical to the behavior 
> experienced when the KI6WX SSB Increased RF Gain mod is added to the 
> KSB2 board, *and* the KPA100 is also in-line.  The result of that 
> combination is that there is more overall RF gain than the KSB2 ALC 
> circuits can handle.  Your K2/100 may have a bit more available RF gain 
> on 40 meters than the average K2.
> 
> The fix for the above is to change the KSB2 board ALC.  1) Cut the trace 
> on the top of the board between P1 pin 6 and the base of Q1.  2) Install 
> a 1k resistor over the previous cut (between P1 pin 6 and the base of 
> Q1).  3) Change the value of R9 to 1.5k.  These changes were first 
> suggested by Gary Surrency of Elecraft support.
> 
> You gentlemen may wish to try this even if you do not have the KI6WX mod 
> installed.  I do not believe it will cause any other difficulties.
> 
> It is a mystery to me why the situation is not present with the display 
> in ALC mode, but then I am not familiar with all the internal workings 
> of the KSB2 firmware.  My guess is that the slight additional load 
> provided when monitoring the ALC level is sufficient to control the 
> overdrive.
> 
> 73,
> Don W3FPR
> 
> douglas.maxwell at virgin.net wrote:
>> Hi All,
>> My K2 ser no. 4688 and KPA100 bought 11/07 work FB on cw.
>> On 40m SSB I have noticed a fault condition with my KPA100. On power
>> cycle or mode change, if the power control is not set to maximum, but set
>> so the KPA100 is 'in-line' say 20w. The power output by the KPA100 will
>> be the full power output i.e. 100w and not 20w. This is correctly
>> indicated on the K2 power meter accompanied with voice peaks coming
>> through the speaker.
>> You can imagine the problems this causes if driving an amplifier.
>> This fault condition can be cured by doing either of the following:
>> 1) Select ALC function on the K2 meter.
>> 2) Whilst talking into the microphone vary the power ctrl to full then
>> back down to the required power level.
>> In both cases the ALC suddenly wakes up and brings the power down to 20w.
>> The worrying thing is that I described this fault condition to another
>> similar ser no K2 owner and he tried and found the same thing happening
>> on his. It's early days yet and we have yet to get together and really
>> nail down the similarities, but I ask you what hardware problem could be
>> sorted by a simple front panel key press? I hesitate before suggesting
>> this is a firmware problem as so many owners have not noticed this
>> before. Please could any K2 owners of a similar ser no try this simple
>> test and post their findings?
>> Doug GM0ELP
>>  
>>  
>>  
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