Jeff, Try measuring the voltage at U2 pin 5 again making certain your probes both have good contact.
The voltage at U2 pin 5 is determined only by a resistor network - if it is still quite low, check the voltage on the 8A line - the output of regulator U4 (upper leg) - it should be 8 volts. If you have 8 volts at U4, then check and re-check the soldering of Control Board RP6, R1 and U2, then remeasure. Remember that the voltage is determined only by a resistive network (which includes the RF Gain pot), there are no active components involved, so if the voltages to the resistors and the connections are proper, you should achieve the correct voltage for the AGC Threshold. Be aware that the voltage for the AGC Threshold may not be optimum for your K2. After your K2 is fully built, aligned, and everything is working properly, you can optimize the AGC Threshold so that the AGC does not become active with no signal into the K2 antenna - so don't be concerned if the 3.8 volts is near the upper limit, I find that the optimum setting will vary from a low of 3.65 volts to a high of 3.78 volts. 73, Don W3FPR > -----Original Message----- > > I've just completed the first alignment and test and everything > checks out except setting the AGC threshold. > > When I put the probe of my DMM on pin 5 of U2 (a hellish place to get > consistent readings) and adjust R1 > I get only .002 DC volts. > > I've resoldered the pins on both U2 and R1. I've looked through > Troubleshooting and the Reflector and > haven't found anything relevant. > > By the way I had no trouble with the S-Meter alignment which is > dependent on the AGC threshold. > > Is there any place else I should look on the control board for a > possible source of trouble, or could U2 or > R1 be defective? (I know components are rarely defective). > > TIA, > > Jeff > > KG6ZVT > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
