[Elecraft] [K3] Resolution - Tuning problem from 1485 to 1585 kHz (AM broadcast)

[Wright, Robert]

Once we determined that the problem was probably particular to my unit,
I ran the synthesizer calibration as Joe suggested - but to no
improvement (wait, there's more - Joe was on the right track).  So I
called Dale Farmer who had me display the PLL voltages (tap "DISP"
button and then turn VFO-B) which read "PLL 1*7.4" while I was tuned to
the range in question - an indication of a PLL problem.  Dale said that
normal PLL voltages were in the 0.7 or 1.0 to 6.5 Volt range.  He
suggested that I rerun the synthesizer calibration with the tighter
manufacturing tolerances (tap "8" as explained on page 61 of the
manual).  This fixed the problem, but running the calibration a second
time brought the problem back.  Clearly we were on the edge of some
tolerance here.  Oddly, the calibration routine never indicated any
error message.

Here comes the fun part.  Dale suggested that I "massage" the toroid on
the synthesizer board.  This consisted of removing the plastic bolt and
ferrite cover (making sure not to drop the brittle ferrite) and then
making sure the bifilar windings were properly spaced and that the third
winding (gold wire with only three turns) was up against the bifilar
windings.  Dale indicated that this needed to be done to some of the
boards in the production process.  Having done that and after
reassembling the toroid cover and rerunning the synthesizer calibration,
the problem was reliably fixed.

Thanks to Joe and all who responded.  I know I learned something and I
hope by writing this up, anyone else who has this problem can benefit.

Bob, N7ZO

-----Original Message-----
From: Joe Planisky [mailto:jplan at jeffnet.org] 
Sent: Monday, October 11, 2010 4:13 AM
To: Wright, Robert
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] [K3] Tuning problem from 1485 to 1585 kHz (AM
broadcast)

Hi Bob.

Try rerunning the synthesizer calibration procedure as described in  
the "Calibration Procedures" section of the manual (page 49 in the D5  
revision).

73
--
Joe KB8AP


On Oct 10, 2010, at 9:38 PM, Wright, Robert wrote:

> I was DXing the AM broadcast band tonight with my K3 when I noticed  
> that
> the received frequency stopped moving as I tuned from 1485 to 1585  
> kHz.
> The dial frequency (VFO-A) continues to change but the received signal
> does not change.  This seems to happen in both AM and SSB modes.  Has
> anyone else noticed this or is this a problem unique to my K3?
> ...
>
>
> Bob, N7ZO