[Elecraft] Hi current/low power out on 20 meters w KPA100

[Ted Turk]

Gregg,

The problem appears to have been a batch of 1.6 ohm metal film 
resistors (R19,20) that had 6 turns and produced a weak 10MHz or 
thereabouts trap with C80,81 (4700pF).  I believe Elecraft have sourced 
some resistors with lower inductance.  For the Brits, locally obtained 
Vishay resistors (Farnell Part No; 550-012) worked.  I could only get 
1.5 ohm in 2W power rating but they had 1.25 turns and therefore only 
1/23rd of the calculated inductance.  After fitting I reset the drive 
bias.  The problem was initially identified by changing C80,81 and a 
temporary cure effected by increasing the values to 5600pF or, in some 
cases, 6800pF.

Scott at parts has the best American solution.

73
Ted G7BQM K2#4732

On 11 Oct 2005, at 01:54, Gregg W6IZT wrote:

> What was the final resolution to the high current/low power out 
> condition? I
> swapped C80 and C81, but this did not cure the problem. I recall 
> someone
> saying that the problem was with  two resistors (r20/21?). Is this the 
> case?
>
> 73
> Gregg
>
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