[Elecraft] KPA100 Upgrade Kit

[Don Wilhelm]

Werner,

If you look at the new KPA100 schematic and parts list (download the new 
manual), you will see that C31 has a value of 0.22 uF.  The KPA100UPKT 
instructions tell you to change the value on the schematic, but there is 
no new C31 included with the kit.

In fact, I was directly involved with testing the newer T/R switch 
design for the KPA100 as a Field Tester and afterward I discovered the 
C31 problem.  Some KPA100s will oscillate at 600 to 800 kHz with the old 
value C31 installed.  I had one of the first updated KPA100 that had 
those symptoms on my workbench and found that C31 was not acting as an 
effective bypass, so the updated value was included for all new 
KPA100s.  It has not made it into the KPA100UPKT yet, but it should be soon.
Not all KPA100s show this problem, but many do, so it is best to change 
C31 while you are adding the KPA100UPKT. 

If you do not want to wait for the part from Elecraft, you can use most 
any 0.22 uF cap rated at 50 volts or more - even 2 0.1 uf caps in 
parallel (one on top of the board, the other on the bottom) will work 
just fine too.

73,
Don W3FPR

Dr. Werner Furlan wrote:
> Where did you get this information? In my KPA 100 Kit C31 was 0.033 µV
> and in the latest manual and in the upgrade kit diagram it is also a 0.033 µV  
> (33N).
>
>
>