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

[CJA]

Don:
I sent the txt below a while back but it must have gotten lost in
cyberspace.  In addition to the measurements below, when I turn on the K2
now I get the full Elecraft in the LCD, a few clicks from relays and the
speaker as well as a steady medium frequency tone.  Nothing works on the
pannel.

BEGIN EMAIL
I disconnected everything and put it aside for a while.  Now I am back to
it.  The measurements are as follows:

Q1 Collector:  6.77 (Fluctuates, The first time I measured it was 7.6)
Q2 Collector:  7.3 (Fluctuates)
Q3 Gate:  .003
Q4 Gate:  7.25

Shorted Q3?  How would it have shorted.  I do not see anything that would
have caused the short.

In addition, once this issue is sorted out, I would like to go through a
complete tune up procedure.  I have the following upgrades in the K2 along
with the KAT/KPA 100 in a separate enclosure:

K60XV (No longer shows up on the LCD), KIO2, K160RX, KNB2, KAT2, KSB2, KBT2

Is there a stem to stern check-up procedure that I can follow?

As always, thanks for your assistance.

Chris Amyes
K7CJA


Don Wilhelm-4 wrote:
> 
> 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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>>   
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