[Elecraft] K2 freeze at startup... need advice

Fri Sep 19 10:16:53 EDT 2008

Jean-Francois,

Saying what happened to U6 is only a guess, but I would suggest static 
damage.  Not necessarily static damage that happened recently, but 
sometime in the past.  However, if you had a nearby lightning strike 
that caused a charge to build on your microphone cable or paddle cable, 
that may be the reason.

One of the aspects of static damage is that it often does not fail 
immediately, but at some time in the future.  I suspect that is what 
happened.
That is why we hear so much emphasis placed on using an anti-static mat 
and a wrist strap when working with active devices.
Electronic devices are becoming more and more static sensitive, which is 
a result not only of the technology used, but also from stuffing more 
and more circuits into a smaller and smaller size.  Before active 
devices are mounted into a circuit, they are quite susceptible and must 
be handled with care.

73,
Don W3FPR

Jean-François Ménard wrote:
> You are right!! After U6 removed.... RP4 pin 5 and 6 are now at 81k ohm!!
>
> U6 must be replaced
>
> Thanks for your help..... But one question remains..... What did 
> happen  to U6 ??
>
> Jean-François Ménard
>
> Le 08-09-19 à 09:52, Don Wilhelm <w3fpr at embarqmail.com> a écrit :
>
>> Jean-Francois,
>>
>> Sounds like you are homing in on the problem.  Try removing the 
>> microprocessor and measuring the resistance between RP4 pins 5 and 
>> 6.  If it is normal (81K), then you have a bad microprocessor input 
>> at pin 30.  If so, replacement of U6 is the only solution I know about.
>>
>> 73,
>> Don W3FPR
>>
>> Jean-François Ménard wrote:
>>> I also found another thing.....
>>>
>>> Resistance check of Pin 7 and 8 of RP4 on the control board give me 
>>> 81K ohm, but PIN 5 and 6 give me 19K ohm... should be 81K ohm too !!!
>>>
>>> Le 08-09-19 à 09:29, Jean-François Ménard a écrit :
>>>
>>>> It seems that a resistence check on the control board give me a 
>>>> hint..... U6 PIN 29 are inside spec, but PIN 30 give me only 16K 
>>>> ohm and should be higher... around 80K ohm to 90k
>>>>
>>>> The key jack seems to be good, R1 and R2 are OK.
>>>>
>>>> Re-insert controler on RF board, nothing change
>>>>
>>>>
>>>> Le 08-09-19 à 08:11, Don Wilhelm a écrit :
>>>>
>>>>> Jean-Francois,
>>>>>
>>>>> It certainly could be a faulty key jack, but it could be a 
>>>>> microprocessor problem too.
>>>>> Turn the power down to zero for further testing.
>>>>> Then check the voltage at the end of R1 and R2  near the key jack 
>>>>> - they are easy to reach if you remove the left side panel.  The 
>>>>> voltage should be near 5 volts if there is nothing pulling those 
>>>>> inputs down.
>>>>> Remember that the DOT line and the PTT line are one and the same 
>>>>> on the K2, so if that line is low the problem nay be in the key 
>>>>> jack or on the Front Panel board.
>>>>>
>>>>> Should you find either the DOT or DASH lines near zero volts, turn 
>>>>> power off and make resistance checks to find out if there is a 
>>>>> short (maybe a solder bridge that has been dormant for a long 
>>>>> time).  Those signal lines run direct to the microprocessor, so 
>>>>> there is only the jacks, PC traces, and the microprocessor involved.
>>>>>
>>>>> 73,
>>>>> Don W3FPR
>>>>>
>>>>>
>>>>> Jean-François Ménard wrote:
>>>>>> It seems that something let my K2 stuck in TX mode. I removed all 
>>>>>> module and put appropriate jumpers (unmod kit). Still in TX when 
>>>>>> powered ON. I checked this using my DL2 dummy load with my 
>>>>>> multimeter.... I always have output power !!
>>>>>>
>>>>>> Could it be a defective KEY jack that is jammed? I have nothing 
>>>>>> plugged......
>>>>>>
>>>>>>
>>>>>> Le 08-09-18 à 23:33, Don Wilhelm a écrit :
>>>>>>
>>>>>>> Jean,
>>>>>>>
>>>>>>> This is strange - the second case of similar behavior reported 
>>>>>>> on the reflector today.  Could it be a case of the 'phase of the 
>>>>>>> moon'?
>>>>>>>
>>>>>>> When the K2 is in transmit state, the behavior will be as you 
>>>>>>> describe - no buttons operate but the K2 displays the frequency.
>>>>>>>
>>>>>>> Check to see if your K2 is somehow stuck in transmit.  The 
>>>>>>> easiest way is to check the state of the 8R and 8T voltages.  
>>>>>>> You can checkby measuring the DC voltage at the anodes of D6 and 
>>>>>>> D7.  During receive, the voltage at D6 anode should be about 8 
>>>>>>> volts and the voltage at D7 should be near zero volts.  If the 
>>>>>>> K2 is 'stuck in transmit', those voltages will be reversed.
>>>>>>>
>>>>>>> If your K2 is indeed 'stuck in transmit', try removing the key 
>>>>>>> plug and the microphone - if something external is creating that 
>>>>>>> transmit condition, it should be OK with those cables unplugged.
>>>>>>>
>>>>>>> 73,
>>>>>>> Don W3FPR
>>>>>>>
>>>>>>> Jean-François Ménard wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Hi everybody,
>>>>>>>>
>>>>>>>> I have my first major trouble since my building experience back 
>>>>>>>> in 2004. Now, everytime i power up my K2, I can see ELECRAFT 
>>>>>>>> and then the frequency..... but everything is frozen 
>>>>>>>> after...... still get the frequency displayed, but no button, 
>>>>>>>> no function work. I also tried to reset the K2 to the factory 
>>>>>>>> default by holding 4-5-6 buttons..... Got the 201 message then 
>>>>>>>> back to the ELECRAFT and the frequency..... but still frozen !!!!
>>>>>>>>
>>>>>>>> Is it possible the the control board PIC got a static discharge 
>>>>>>>> or something like this !?!?!?!
>>>>>>>>
>>>>>>
>>>>>> ============================
>>>>>> De Jean-François Ménard / VA2SS
>>>>>>
>>>>>>
>>>>>> ------------------------------------------------------------------------ 
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>
>>>> ============================
>>>> De Jean-François Ménard / VA2SS
>>>>
>>>>
>>>>
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>>>
>>> ============================
>>> De Jean-François Ménard / VA2SS
>>>
>>>
>>>
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