[Elecraft] KPA-100 pop from TX to RX

[Don Wilhelm]

Dave,

If it does not have the popping sound when you select 8R=nor, then run 
it that way.

With the updated KPA100, there is one resistor on the bottom of the 
board - a 22k from the +12 volt rail to the drain of Q7.
What a 100k resistor would be doing on the bottom of the board, I have 
no idea.  Perhaps it is contributing to your popping condition.

The KDSP2 has mute transistors and apparently the unmute time for them 
(in addition to the audio delay through the DSP) is causing that pop to 
be heard.

73,
Don W3FPR

On 7/3/2013 11:09 PM, DaveVK wrote:
> Don,
>
> I have fixed the mechanical buzz from the SSB tx on the KPA-100.  The fault
> was mine.  Across the RF Aux input between the PCB and the heatsink there
> seems to be a blue resistor with the colours Brn-Blk-Blk-Org-Brn with one
> leg that was touching the heat sink.  The legs are long and so I just pushed
> it away with a screwdriver.  I don't know what that part is doing there, or
> why it is installed like a hack did the job but the memory of it is lost in
> history.
>
> I cannot find the part listed in the KPA instruction manual or any of the
> upgrade kits. So maybe it doesn't belong there??!!  But anyway, that problem
> is fixed and the next time I'm in a position to remove the heatsink I'll
> install that part properly.
>
> I seem to have the upgrade kit installed and the blue cores are in the
> KPA-100.
>
> Now the popping is unsolved.  It seems to be connected to the DSP.   The
> popping is most prominent on bands below 20m.  When the DSP is bypassed the
> popping disappears.  I am still hunting this one down.
>
>