Thanks to everyone who replied! Wow, help sure comes in a hurry on
this list!
The general consensus appears to be that I'm ok for the time being
(yay!), so I'm going to go ahead and move on.
I did test with the internal voltmeter as well, and it reports 3.5V.
Special thanks to VE3TIX who asked if my DMM batteries are fresh...
no, they weren't! I replaced the battery and the display is a lot
easier to read now, thanks! Sadly, it still reports 3.59V.
Although I am starting to wonder about the general advisability of
relying on a meter that came free with my oscilloscope. :-)
Also, in the process of fiddling with things, I discovered that my
little bench power supply is very noisy! I was using my Yaesu VX-7R
as an ad-hoc RF probe; K4DGW sent me a link to a message from Don
Wilhelm in the list archives which got me thinking about noise, so I
grabbed the Yaesu to try to use as an RF probe, and discovered lots
of noise on 7MHz, 10MHz, and probably everywhere else (!), which went
away completely when I switched off the power supply! I rigged a
bunch of D batteries for 12V and powered the K2 with that instead; it
worked fine, the noise went away, but the AGC reading still wouldn't
go over 3.59v.
But I think I'm going to need a power supply... any recommendations?
I can probably try to stop by HRO tomorrow.
Oh, and if anyone has a recommendation for a high quality but fairly
inexpensive DMM, I'd be interested to hear about that too...
Thanks again everyone,
Sarah AF6FH
On Fri, 2007-11-23 at 12:53 -0800, Sarah K. wrote:
Hi,
I'm Sarah, AF6FH! I just got my license a couple weeks ago, and I'm
now assembling K2# 0622, which will be my first HF radio. I started
assembly on Wednesday night, and so far, everything's been going just
fine.
But...
I'm having a little issue with setting the AGC Threshold.
The instructions (pg. 48) say to set the RF GAIN control fully
clockwise, measure the voltage on pin 5 of U2 on the control board,
and adjust trimmer R1 for a reading of 3.80 volts.
I did my voltage measurements with my own (cheap) DMM, not the
internal voltmeter.
My concern is that, by adjusting R1, the highest I could get the
voltage to go was 3.59v, so for the moment, that's where it's set.
I measured the voltage on the LM29307-8, and it has 12.23V at the
input, but only 7.53V at the output. The 78M05 has 4.93V at its
output.
When I rotate the AF GAIN control, I get a range of 4.68V (fully
counter-clockwise) to 3.59V (fully clockwise) on pin 5 of U2.
My power supply is a small benchtop power supply; it's putting out
12.4V, and reports the K2 is drawing about 100mA. When I measure the
input voltage across the K2 input jack, I get the same 12.4V.
All of the previous checks were fine, and the following step, S-Meter
Alignment, seemed to work just fine.
So, my question is, do I have a problem? Should I be concerned?
Thanks,
Sarah AF6FH
_______________________________________________
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
