[Elecraft] Re: KPA100 question

[Ron ZL1TW]

Hi Rob,
             Your problem sound a bit different. What was happening on 
quite a few earlier KPA100's was the diodes in the switching circuit were 
providing enough capacitance to cause a tuned circuit with RFC3 and that 
circuit would break into oscillation and modulate the carrier with a 
spurious signal. The resulting signal then had nasty sidebands and I used 
to get accused of "Splatter". It used to occur at powers above about 80w. 
mainly. The fix was to dampen RFC3 with a 1k resistor as well as a resistor 
change in the high voltage bias supply to make sure the HV supply didn't 
drop too low on demand.
The changes are outlined in the "K2/100 Manual ( Appendix G) ERRATA"   rev. 
C-3, December 14, 2004.  ( steps 1 and 3 )  which is obtainable off the 
Elecraft Web site.
Hope this helps?
Cheers.......Ron ZL1TW

At 07:20 AM 4/24/2005 -0700, you wrote:
>What are the symptoms of the oscillation? My KPA100 sometimes loses 
>connectivity with the K2 and the communications between them is lost. Only 
>fix is to power them both down. Don't know where to start looking for the 
>problem. RFI?
>
>-rob N7QT
>----- Original Message ----- From: "Ron ZL1TW" <ron_w at clear.net.nz>
>To: <elecraft at mailman.qth.net>
>Sent: Sunday, April 24, 2005 4:15 AM
>Subject: [Elecraft] Re: KPA100 question
>
>
>>Hi,
>>      Just my 2c worth......in the days before the stray oscillation that 
>> occurred in *some* KPA100's was found and a fix presented, I was advised 
>> by Gary to try mounting  my C83 on the *TOP* of the ends of the 1 and 3 
>> "winding" of T2, and it is still there lying parallel with the PC board, 
>> so having it slightly off vertical in the suggested position shouldn't 
>> matter a fig I imagine.
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