[Elecraft] K2 -- Erratic behaviour. Display changes and locks up

[Don Wilhelm]

Colin,

The E13.8 0.26 display is the voltage and current being drawn.  When working
properly, the K2 will show that display when the DISPLAY button is tapped.
Likewise the ST L 071 is your sidetone level, and quite likely the PF1
button is set to bring up that display.

What I am saying is that those displays indicate that the microprocessor
'thinks' a button has been pressed - apparently some glitch is giving the uP
that input.  The 'freeze-up' is a result of processing what the uP thinks is
a button input - all operation is dedicated to processing that button press.
You can demonstrate that easily by pressing and holding the PF1 button
(assuming that it is set to ST L), as long as you hold that button in, all
other buttons (and VFO knob too) are ineffective (except the OFF switch
<G>).

First thing to do is check carefully to be certain all the pushbuttons are
operating mechanically (push them in and see how they feel), you should
sense a slight tactile feedback sensation as the switch contact is made, and
whil checking the pushbottons be certain none are binding against the front
panel, they should all operate freely.  You can do this test with power off,
it is not an electrical test.

Conditions like this could be caused by a loose or oxidized connection, so
remove the Control board and front panel and plug them back in - just
working the connector by replugging it is usually sufficient to remove any
oxidation.  Do the same thing with the microprocessor itself to clean its
pins and the socket.

Lastly, such conditions can be caused by an unsoldered connection - granted
it worked for a long time, but sometimes an unsoldered connection can sit
there and make contact for years until finally enough oxidation builds up to
cause it to fail.

Intermittent problems of this nature are elusive and difficult to
troubleshoot - partly because on never really knows if it is fixed.  As an
aide to troubleshooting, make notes of the behavior (including what you were
attempting to do just before the trouble became obvious), and with a
collection of these symptoms, often a pattern can be seen which helps to
localize the source of the problem.  It certainly would be nice to be able
to make measurements and catch the bad condition 'in the act', but they
often disappear and work correctly when they are approched with a probe of
any type - nasty problems where you just have to make a 'best guess' and
give it time to see if it was really fixed.  Making notes of strange
behaviors is often helpful because this form of troubleshooting can take
weeks or even months to finally identify the real failure point.

73,
Don W3FPR


> -----Original Message-----
>
> I am a new owner of an early K2  with Seriel No 638. Initialy rig
> worked fine, but now a random fault is occuring .
>
>   I hear a couple of relay clicks (sometimes more) and the
> display rapidly changes and when stops,  the message  E137 0.26
> or E138 0.26 is usualy given. On one occasion the display was
> left with St L 071. On other occasionns the display just appears
> random. Are these error codes, and if so could anyone give me
> their meaning.  The push buttons are non-functional and I can
> only get back to operation by switching OFF , and then ON.
>
>   To me,  the symptoms are similar to my early computer
> experiences, when the computer went south.  Any recommendations
> for trouble shooting would be appreciated.
>
>   The last point is that the problem is chronic during warm up.
> After 15 to 20 mins the problem is either gone or significantly
> reduced in magnitude.
>
>   Thank you, Colin M3WCK
>