K2 -- Erratic behaviour. Display changes and locks up

[C WEAVING]

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
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[Ron D'Eau Claire-2]

Don, who has probably fixed/built more K2's than would fit in my house, may
know of some concrete suggestions, but you can start by checking ALL the
solder joints, especially on the control board.

Probably the most common cause of a "failure" in a K2 that hasn't been
abused will prove, over time, to be a missed or "cold" solder joint.
Elecraft uses plated-through holes, so the wire laying in the hole will make
good enough contact for a long time, even several years, before enough
oxidation builds up to cause the circuit to open. Then, when it does, it'll
be very sensitive to things like temperature that cause things to move about
just a tiny bit, greatly affecting the resistance of the unsoldered joint.

Tapping on the case would seem to be a sure way to identify a loose
connection, but that's not always true. Many parts are tiny and don't have
enough mass to move enough relative to the board when the case is bumped.
Besides, the fault produced by a loose part is often dependent upon
something else going on at the same time that causes that circuit to
misbehave, and tapping at other times would show no symptoms.

There's the time-honored technique of poking at each part with the rubber
eraser end of a pencil, but again you would have to know what else must be
going on to cause the fault to occur for that to work. That's why I suggest
scouring the board with a strong light and magnifier, one solder pad at a
time, looking for either a cold solder joint or a missed solder joint.

Actually, there's one thing I'd do first that harkens back to the early
computer days you mentioned and why Elecraft avoids I.C. sockets when they
aren't necessary: taking ESD precautions, unseat and reseat the firmware to
make sure it isn't a bad contact between one of the pins and the socket.
I've not heard of that happening on any Elecraft gear so far, but I don't
trust sockets beyond the first sign of an intermittent problem.


Ron AC7AC


-----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 _______________________________________________

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[Don Wilhelm-3]

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
>

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[Geoffrey Mackenzie-Kennedy-2]

Colin,

My K2 #3255 shut down one day when about 2-1/2 years old leaving the display
showing the frequency last used, but none of the front panel controls
functioning except the power ON-OFF switch. After an overnight rest all was
well. Eventually I found the problem to be caused by the socket of the
Control Board MCU, perhaps a bit of corrosion, and later I replaced the
socket with a turned pin type for a lasting solution.

73,
Geoff
GM4ESD

C WEAVING  [hidden email] wrote:

>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

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