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Re: KPA100 question

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Ron ZL1TW

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.
Putting the 1k resistor across RFC3 fixed the oscillation problem, and I
never bothered to put C83 back in it's proper place. My KPA100 works fine.
( now)
Cheers.....Ron ZL1TW

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Ron ZL1TW

Re: Re: KPA100 question

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" <[hidden email]>
>To: <[hidden email]>
>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.

.........................snip ........snip.............
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