[Elecraft] [K2] Setting the AGC Threshold Section of Build

[Don Wilhelm]

Don. measure the voltage at the output side of Control Board 4.  It 
should be in the vicinity  of 8 volts.

I would suggest removing the 15k resistor and checking the voltage at CB 
U2 pin 5.  If that voltage is 3.7 volts or more, that will work out just 
fine.  If lower than 3.7 volts, add back the resistor and set he AGC 
Threshold voltage for somewhere between 3.75 amd 3.8 volts as measured 
at Control Board U2 pin 5.

73,
Don W3FPR

On 8/24/2012 8:39 PM, Don Singer wrote:
> I am finishing the first phase of my K2 build, and everything has gone
> well up to this point. All resistance and voltage tests are fine.
>
> When I went to set the AGC Threshold as per page 47 of the K2 Manual, I
> got 5.0 volts as the lowest setting I could achieve when adjusting R1 on
> the Control Board , so I followed the instructions at the top of page 48
> and followed the AGC Level Application Note and installed the 15K
> resistor between pins 3 and 4 of RP6 on the Control Board.
>
> The resistance across the 15k resistor, once installed on the Control
> Board on pins 3 and 4, was 3K. I reflowed the solder to see if I could
> get the 3.5k ohms specified on the worksheet, but still got 3K and
> thought that is good enough.
>
> I reassembled the K2 and ran the AGC Threshold section again - but,
> instead of being closer to 3.8 volts, I am now at 6.2 volts as the
> lowest reading I could get. The lowest voltage went up and not down? Why
> is that?
>
> I am not sure if this is meaningful or not so I am holding from moving
> forward until I know if this is an issue, or just move on, or remove the
> 15k resistor across pins 3 and 4 of RP6?
>
> Thanks,
> Don KF7DS
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