[Elecraft] [K3] Strange Selective Hearing in My K3

[Eric Fitzgerald]

    I supposed in any lengthy marriage a selective ear or a biological
    mute button, so to speak, becomes inevitable ...or so it would
    appear with my aging K3, purchased in 2009.

    Here are the rather perplexing symptoms:

    After the K3 has been on a while all signals and noise disappear. 
    The radios shows consistent s1 or 2 white noise. This is true on all
    bands, all modes and with the preamp, agc, noiseblanker, etc on or
    off. After turning the radio off for an hour or more, all signals
    return as normal - only to disappear again after an indeterminate
    period of time. I'm guessing that there is some failure that is
    affected by the component in question heating up.  I use this radio
    in receive almost 24/7 monitoring the bands. Perhaps she is just
    tired of listening for me? ;-) Any ideas what this might be?  Stupid
    operator error is never out of the question around here.  I thought
    I would ask in here before bugging Elecraft service in case I'm
    missing something easy.

    TIA

    Eric KG6MZS

    www.kg6mzs.com

I should add that when I transmit a tone from WJST-X, say, the red light comes on the K3, one bar lights up on the K3's RF meter but no power or SWR is registered on my external meter.

So that would seem to eliminate anything disconnected from the rear panel connector via an intermittent connection.  If that were the case, I would expect to see a "High SWR" reading before the power folded back.

Eric