[Elecraft] Intermittent RXsensitivity...

[Don Wilhelm]

Gerald,

That certainly sounds like it might be hard to isolate.
I may be wrong, but from the behavior it sounds like you have a relay with
points that are not making good contact - when you put a bit of RF through
it, it becomes OK for a while.  Please be aware that this is just
speculation on my part.  You may have to work with it a lot to determine if
it is really fixed.  Intermittents are very difficult to troubleshoot.

Before you do anything drastic, check for unsoldered connections in the
bandpass and lowpass filter areas and the T/R switch too.  Sometimes
unsoldered connections will work just fine for a long time but afterward
they begin to develop oxidation which makes the connection first
intermittent and then perhaps fails completely.  The connections for these
areas are under the heat sink, so be prepared to remove it for your
soldering checks.

If you can induce the failure and then have it continue while you remove the
heat sink, you could also check the relay points with a continuity test
between the pins.  Check the schematic key for the realy chart and the
schematic itself for the appropriate relay points and pins.

You should be able to receive with the heat sink removed, but be certain you
do not attempt to transmit until it is replaced - WORK CAREFULLY if you
attempt power on with the heat sink removed.

73,
Don W3FPR


> -----Original Message-----
>
> Hi all
> I notice an intermittent rx sensitivity on my K2, Serial-Nr.
> 488, after changing band eg. from 20 to 40 and vice versa. After
> pushing tune or transmitting a couple of dots the sensitivity
> returns
> on the activ band and is gone on the other band. This happens with
> and without the KAT2.
>
> Where shall I start searching?
>
> 73 Gerald, HB9CEY
>