[Elecraft] AGC Threshold question - K2

[W3FPR - Don Wilhelm]

Neil,

Yes you apparently have something wrong.

The voltage measurement comes from a purely resistive network fed by 8 
volts, and there is not much to troubleshooting it - that is if you can 
manage to probe the pins of R-Pak RP6.

With the RF gain in the full clockwise setting, you should read close to 0 
volts on pin 6 of RP6 - and you should find 8 volts from the power source on 
pin 3 (of RP6).  The voltage at pins 4 and 5 should be at the same voltage 
as pin 5 of U6, and the voltage should be adjustable by changing R1.  The 
voltage on pin 7 of RP1 will depend on the setting of R1.  Check out the 
schematic of the Control Board - look in the AGC section in the lower left 
corner to see how these resistors are connected.

If you find a voltage that is unusual, first check the soldering, and next 
be certain RP6 is the 5.1k package (the numbers 512 should appear in the 
labeling).

If the voltage on pin 3 of RP6 is much lower than 8 volts, the 8 volt 
regulator (U4) may be the problem.  However, the last person I helped who 
had a reading similar to yours did not have the probe on pin 5 of U6.  Pin 5 
is the topmost pin and toward the side panel.

73,
Don W3FPR

----- Original Message ----- >
> I am just at the first alignment and test stage of my K2. Everything 
> checked out just fine except the step where I am to adjust R1 on the 
> control board for 3.80 v on pin 5 of U2. The highest I can get the voltage 
> to go is 3.38v. Is this something to worry about? If so, any clues?
>