[Elecraft] K2 Assembly Question

[DW Holtman]

Hello,

I want to thank all of the help I received on this problem.

The AGC adjustment problem was solved by replacing the 8.0VDC  regulator 
with one that puts out 8.0 volts not 7.5 VDC..

I also had a problem where the MCU on the control board sometimes would not 
start, it just froze and all controls were inop. I found an un-soldered 
(surprise surprise) connection.

Not I have a new problem, and was wondering if anyone has any ideas.

As I started the alignment and test Part II. everything went fine until I 
got to the 4th step on the left column on page 64. There is no output on the 
left hand side of R-30.

I traced this back to U5 (I think) The voltage does not vary on pin 7 of U5 
as the frequency is varied. It stays at VCC, 5 VDC. I think this changing DC 
voltage must be there to make U4 and U6B operate to get the voltage on R-30. 
Am I wrong on this, very little to no experience working on PLL 
Synthesizers.  All of the other voltages on U5 look good. Any suggestions on 
where to go from here. The PLL reference oscillator is working, clean signal 
at around 12.096 MHZ.

It might be a soldering problem, but I really do not think so, I have spent 
a lot of time looking closely at solder joints.  I will keep checking and 
re-heating the solder joints.

Any suggestions on what to check would help.

Best,
DW Holtman
WB7SSN

----- Original Message ----- 
From: "DW Holtman" <tubestuff at comcast.net>
To: <elecraft at mailman.qth.net>
Sent: Wednesday, February 20, 2008 7:25 AM
Subject: [Elecraft] K2 Assembly Question


> Hello,
>
> I'm in the middle of building a K2, S/N 6412.
>
> I have a couple of questions, hopefully some of the knowledgeable Elecraft 
> people on this forum can help.
>
> While doing the Alignment and test Part 1, I had a couple of readings that 
> were not in specs.
>
> 1. Page 48, Setting the AGC Threshold, the manuals calls for adjusting 
> R-1 for a reading of 3.80VDC on pin 5 of U2. The highest R1 would adjust 
> to is 3.60VDC.
>
> 2.  Page 48 Bargraph Current test. The manual calls for a current reading 
> of 0.16 to 0.18. My K2 reads 0.25 amps. That is quite a bit higher than 
> what is called for.
>
> Any suggestions? Are these readings anything to worry about?
>
> Thank you in advance for any help.
>
> Best,
> DW Holtman
> WB7SSN
>
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