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K2 / 10 - Freeze Up

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Joe Smith-15

K2 / 10 - Freeze Up

Earlier this summer picked up a very nicely built K2
to replace the one I had built and foolishly sold. S/N
is 4715 and the build date is 2/05. Firmware is 2.04P
1.09. Installed accessories are K160RX, KAF2, KAT2,
KI02, KSB2, and KNB2. Additional modifications are the
W3FPR AF Level Output and Cliffton Laboratories Z10000
Broadband Buffer Amplifier (used with a SDR-IQ to
provice external pan-adapter). The K2 has been used in
the CW mode only.

In the last several weeks have experienced a freeze-up
almost every time used. Will have completed my side of
QSO and received without any problem the other party.
Upon their turnover discover that I have no transmit.

The display will generally be showing power but,
sometimes keyer speed and no amount of control
twisting or button purshing will effect any change.
Recycling power will yield "ELE" in the display but,
otherwise the rig is totally non-functional.

After several hours, can turn K2 back on and all is
apparently normal.

Any ideas would be much appreciated. Have not yet
reset EEPROM to factory defaults.

72, Chuck AF4PP

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Geoffrey Mackenzie-Kennedy

Re: K2 / 10 - Freeze Up

Chuck,

My K2/100 #3255 built in 2003 has behaved in a similar fashion twice, the
first episode taking place in 2005 after the rig had been in "receive mode"
for several hours. The only front panel control that had any effect was the
power ON-OFF switch.

In my case the problem was caused by the socket used with U6, the MCU on the
Control Board. Pulling and reseating U6 cured the problem, which made me
suspect that corrosion had built up on one or more of the socket's contacts.

After the second episode many months later I changed U6's socket to a Turned
Pin type, a type of socket that I should have used when building my K2. I am
not suggesting that you make this change, but I want to alert you to the
fact that the type of socket supplied with the kit can cause problems due to
corrosion of the contacts.

73,
Geoff
GM4ESD

Chuck AF4PP wrote on Thursday, September 11, 2008 at 6:57 AM

> In the last several weeks have experienced a freeze-up
> almost every time used. Will have completed my side of
> QSO and received without any problem the other party.
> Upon their turnover discover that I have no transmit.
>
>
> The display will generally be showing power but,
> sometimes keyer speed and no amount of control
> twisting or button purshing will effect any change.
> Recycling power will yield "ELE" in the display but,
> otherwise the rig is totally non-functional.
>
> After several hours, can turn K2 back on and all is
> apparently normal.

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Don Wilhelm-4

Re: K2 / 10 - Freeze Up

In reply to this post by Joe Smith-15

Chuck,

From your description of the failure indications, I would say that for
some reason or another, the microprocessor is simply stopping.

A reset to factory defaults should be done only as a last resort and
*only* after recording all your menu settings, including your filter
setup data. You will need to restore those settings after a reset.

Behavior like that is related to the microprocessor. Since it is an
intermittent, one never knows when it is cured. *I hate
intermittents!*. When you try to cathc the problem 'in the act', you
will touch something that makes it work again, so you can only guess as
to the source.
For the 'low cost fix', I would recommend doing these steps - in order,
and after each one, use it for a while to see if the problem has
disappeared.
1) Remove and reseat the microprocessor to wipe oxides away from the pins.
2) Reflow the solder on the microprocessor socket. You may want to
consider removing the existing solder and re-soldering it.
3) Replace the 4 MHz crystal - you might have a balky crystal that just
quits.
4) Replace the microprocessor socket
5) Replace the microprocessor itself.

If you want a quick cure, replace the crystal, the microprocessor and
its socket all in one fell swoop - but there is still the off chance
that there is a bad solder connection somewhere else on the Control
Board that is causing the failure.

As Geoff pointed out, use of a machine turned pin socket at U6 would be
a good idea especially if you are in an environment where oxide buildup
is accelerated. Machine turned pin sockets provide a gas-tight fit to
the chip leads where other type sockets do not.

73,
Don W3FPR

Chuck wrote:

> Earlier this summer picked up a very nicely built K2
> to replace the one I had built and foolishly sold. S/N
> is 4715 and the build date is 2/05. Firmware is 2.04P
> 1.09. Installed accessories are K160RX, KAF2, KAT2,
> KI02, KSB2, and KNB2. Additional modifications are the
> W3FPR AF Level Output and Cliffton Laboratories Z10000
> Broadband Buffer Amplifier (used with a SDR-IQ to
> provice external pan-adapter). The K2 has been used in
> the CW mode only.
>
> In the last several weeks have experienced a freeze-up
> almost every time used. Will have completed my side of
> QSO and received without any problem the other party.
> Upon their turnover discover that I have no transmit.
>
>
> The display will generally be showing power but,
> sometimes keyer speed and no amount of control
> twisting or button purshing will effect any change.
> Recycling power will yield "ELE" in the display but,
> otherwise the rig is totally non-functional.
>
> After several hours, can turn K2 back on and all is
> apparently normal.
>
> Any ideas would be much appreciated. Have not yet
> reset EEPROM to factory defaults.
>
> 72, Chuck AF4PP
>
>
>
>
>
> _______________________________________________
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> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
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