[Elecraft] K2 - CONTROL PANNEL FREEZE UP (K7CJA)

[Don Wilhelm]

Chris,

Keep that dummy load attached, and set the power knob to zero.  That K2 
is going into transmit, so you want to protect the PA from harm while 
figuring out what is going on.

Remove anything that may be plugged into either the paddle jack or the 
mic jack and try again.
If it still goes into transmit, remove the top cover and on the Control 
Board, check the collector of Q1 - it will be between 7.5 and 8 volts if 
the K2 is in transmit.  Also, check the collector of Q2, which should be 
at 7.5 to 8 volts during receive, If both Q1 and Q2 have voltage on the 
collector, it is trying to transmit and receive at the same time, so 
keep the power on intervals short if that condition is present.

Assuming you have the 8 volts at the collector of Q1 but near zero at 
the collector of Q2 (proper for transmit state), then check pins 29 and 
30 of Control Board U6 (the microprocessor) - both should be higher than 
4 volts (close to 5 volts).  If one or both are at a low voltage, there 
is something holding the dot or dash lines low, and you should be able 
to locate it with an ohmmeter and visual inspection for solder bridges 
or stray wire clippings.

If you have both transmit and receive 8 volt lines (collectors of CB Q1 
and Q2), then check the gates of CB Q3 and Q4.  For receive, the gate of 
Q4 should be high (4.5 to 5 volts), and the gate of Q3 should be near 
zero.  If these last conditions are true, the microprocessor outputs for 
transmit and receive are correct and the most likely failure is a 
shorted Q3.

Let us know the results of those tests.

73,
Don W3FPR

CJA wrote:
> I have a K2 with a KPA100 and KAT100 in a separate enclosure.  It had been
> working on my lossey loop but I decided to try a ground mounted Hi-Q 4/160. 
> After connecting the antenna, I began trying to tune to the various bands. 
> It seemed to be tuning to a low SWR when the control panel just froze up. 
> The VFO would not change the freq and none of the buttons functioned.  I
> turned it off and on several times and came up with the full elecraft in the
> LCD and then the last freq I was on.  The control panel was still frozen.  I
> then tried to reset.  That did not work.  Now it just goes through the POST
> (full elecraft in the LCD) and seems to go into transmit (dummy load
> connected) with a high pitched tone and hangs there.  Any suggestions would
> be greatly appreciated.  73, Chris Amyes, K7CJA
>   
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