[Elecraft] K2 BFO drift problem

[Don Wilhelm]

Just get a new rubber bumper.  Not only does that glue make a mess of 
things, but it has potential for changing the inductance.

73,
Don W3FPR
On 4/15/2014 5:35 PM, TheMG . wrote:
> I've put a piece of paper under the bumper and re-installed L33 held
> tightly down against the board (pushing the resistor down so it holds
> it tightly).
>
> No observed drift in frequency after a couple hours other than the
> normal temperature-related drift (about 10Hz downward).
>
> This does seem to confirm that the bumper conductivity was in fact the problem.
>
> Looks like I will need a new rubber bumper. I'm not sure what happened
> to this one to make it conductive, but it's definitely not something I
> did as I did not use any cleaning chemicals when initially building
> the K2 (not even alcohol).
>
> I'm also considering just securing L33 in place with a dab of
> electronics-grade silicone and leaving it at that. Although Elecraft
> does not recommend it I don't see how it would be a problem if the
> proper type of silicone is used that is non-corrosive, non-conductive,
> designed specifically for electronics use. If it's good enough for use
> in aircraft electronics... it ought to be fine for this. Of course, it
> would make it slightly more difficult to remove L33 in the future if
> for some reason it was ever necessary to remove it, but not
> impossible. I'm not too worried about that.
>
>