[Elecraft] K2 BFO drift problem

[TheMG .]

Leads under L33 are flush cut as flat as possible and it is mounted on
the rubber bumper with half the stem cut off exactly as per the
instructions. The resistor was pushed down into the center to keep L33
secure and to prevent the resistor body from being pressed on by the
bottom cover.

No luck on resoldering L33 or the crystals underneath it. However I
did notice that when I pull up on the resistor so it isn't pressing
down on L33 (the inductor is at this point completely loose and free
to move around. I have the K2 upside down with the bottom cover
removed and it has been running this way for several hours with
absolutely no drift. BFO range is 4912.31 to 4917.85 and stays within
0.01 of that as it warms up.

It's like there is a couple of turns on the inductor that are ever so
slightly shorting together and only when it is being held/pressed down
onto the rubber bumper. Looks like it may be time to obtain a new
L33...

On Sun, Apr 13, 2014 at 1:46 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
> That indicates that you should concentrate on L33 and things around it.
> "Nudging" things and finding significant changes indicates a bad connection
> somewhere and/or possible shorted turns.
>
> Did you flush cut the leads on the RF board under it?
> Is it mounted on the rubber bumper?
> Did you cut half of the tip on the bumper off?
> The resistor is effectively an insulator, and also provides mounting
> stability.
> After soldering the leads to the board (and to the L33 wires), you should
> push the resistor body down into the center of the toroid to secure L33
> tightly.
>
> Resolder the resistor leads and the leads of L33 again to see if that helps,
> If not, request a replacement L33 and the resistor to mount it.  It does
> sound like there is something amiss with L33 - or the soldering of the
> crystals under it.  Before mounting a new L33, re-flow the soldering below
> it.
>
> 73,
> Don W3FPR
>
>
> On 4/13/2014 2:45 PM, TheMG . wrote:
>>
>> Well, I messed around with it a bit more and I gave L33 and very light
>> nudge with the plastic tuning tool while looking at CAL FCTR. This
>> caused the BFO frequency to suddenly jump down from 4913.30 to
>> 4912.42.
>>
>> Strange thing is, only a few minutes after nudging L33, the BFO
>> frequency had already drifted 100Hz up and still drifting. I give it
>> another nudge and it drops down again but then eventually resumes
>> drifting upward.
>>
>>
>