Don I worked with him last night, he has it all going it was a cold solder
joint on RP6 so he didn't have the 8 volt line. He's got it working
now....we emailed off the list. (Sometimes I forget to hit the reply all.)
Gregg R. Lengling, W9DHI, Un-Retired
K2/100 SN 3075
http://www.milwaukeehdtv.org
----- Original Message -----
From: "Don Wilhelm" <[EMAIL PROTECTED]>
To: "jrb" <[EMAIL PROTECTED]>; <elecraft@mailman.qth.net>
Sent: Monday, December 19, 2005 7:45 AM
Subject: RE: [Elecraft] Setting the AGC Threshold on K2
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
_______________________________________________
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