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

Wed Nov 4 11:17:14 EST 2009

Chris,

The email may have arrived while I was on vacation a week ago - yes, I 
missed it..

Are you certain you measured the gate of Q3 and Q4?  Those voltages are 
normal at the drains of Q3 and Q4 for a K2 in transmit.  You can check 
U6 pin 27 (5 volts during transmit, 0 during receive) and pin 28 (5 
volts during receive and 0 during transmit).

If my guess is correct and you actually measured the drains of Q3 and 
Q4, then you do have a problem with Q2 or its associated resistors in 
RP1.  You should not have 7 volts on *both* Q1 and Q2 collectors (if you 
measured the emitters instead, you will find 7 to 8 volts on both.

Put that aside for a moment (that information will not solve your 
primary problem).  Does the tone sound anything like sidetone?  What I 
am getting to is that - from all information I have right now, that K2 
is going into transmit right after a power on.  That will make the 
buttons inactive, and you first need to find out what is causing it to 
transmit after turning it on.  Once that is solved, you can go on to 
other things.

Keep a dummy load connected and the power knob turned down to zero.

Measure both U6 pins 29 and 30.  Both should be at or near 5 volts - if 
either of them are close to zero, something is keying your K2 and you 
need to find the source. 
OTOH, if both are at 5 volts, the K2 should not be going into transmit 
(unless the TUNE button is stuck on).  If all those things are good, I 
will recommend (I don't do this often) that you do a Master Reset - hold 
buttons 4, 5, and 6 in while turning the K2 power on.  You will know the 
reset has been successful if you see Info 201 in the display for a brief 
time and after that ELECraFT is displayed.

You on the complete check-out - look on my website www.w3fpr.com for the 
K2 alignment document - that is the alignment instructions extracted 
from the manual.  After completing those alignments, then go to the K2 
Dial Calibration article there and do all the steps including the filter 
alignment - the Master Reset will have set all your filter and menu 
setting back to factory default (that is why I do not often recommend a 
Master Reset, and it rarely solves anything).

Make certain your K60XV is properly plugged into its headers and check 
the secondary menu to be certain the menu parameter for D19 is set to "Y".

73,
Don W3FPR

CJA wrote:
> 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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