[Elecraft] K2 Transmitter Power Issue, K2 s/n 4276

[Don Wilhelm]

William,

Is the DC voltage also fluctuating?  If so, your power supply or the 
connecting cable may be the cause.  Also make certain you have a good 
coax between the K2 and the dummy load.  If you have the KAT2 or KPA100 
installed, check the shield of the input coax to be certain it is not 
broken at either the board end or the cable end connector.  Are the 
crimp pins properly inserted into the housing?  The small locking tabs 
should be latched into place in the housing and if properly assembled, 
you can move the crimp pin slightly in the housing.

If it is not the power supply nor the coax assemblies, then the easy 
part of diagnosing your problem is over and it is time to do some real 
troubleshooting to determine the source of the fluctuation.
Strip down to the base K2 (remove the KPA100 or KAT2 if these are 
installed) and connect the K2 to a dummy load.
Then with an RF Probe in hand and the K2 power level set to 5 watts, 
check the RF voltages at each of the points listed starting with the 
middle of the 1st column of page 14 in Appendix E of the manual.  Find 
the first point in this list where the RF voltage fluctuates and let us 
know which point that is.

73,
Don W3FPR

kc4wvl wrote:
> K2 s/n 4276
> Firmware Revision(s):  2.04P  1.09
>
> Finally had time to open up the rig and check the soldering and check the
> placement of the components on the back of the control board.
>
> Still no change. When transmitting, again the power output fluctuates
> rapidly and the current draw fluctuates as well.
>
> Help!
>
> 73 de KC4WVL
> William Smith
>
>
> ----- Original Message -----
> From: "Don Wilhelm" <w3fpr at embarqmail.com>
> To: "kc4wvl" <kc4wvl at peoplepc.com>
> Cc: <elecraft at mailman.qth.net>
> Sent: Tuesday, December 11, 2007 17:01
> Subject: Re: [Elecraft] K2 Transmitter Power Issue
>
>
>   
>> William,
>>
>> Check the soldering carefully, particularly on the Control Board.  Also
>> check and re-check the placement of the components mounted on the back
>> of the Control Board (they are part of the power control circuits).
>>
>> Check soldering, then re-check the soldering, and when that is finished,
>> check the soldering.
>>
>> Good luck in finding it.
>> 73,
>> Don W3FPR
>>
>> kc4wvl wrote:
>>     
>>> K2 s/n 4276
>>> Firmware Revision(s):  2.04P  1.09
>>>
>>> I am having a problem with output power stability. Example: Power set to
>>>       
> 5 watts. When transmitting (into a dummy load), power out is all over the
> place, from as low as .2 watts to as high as 12 watts. This fluctuation is
> very rapid. Measured current (at the P/S) fluctuates with the power output
> fluctuation.
>   
>>> Can anyone give me an indication of any possible cause and solution?
>>>
>>> Thanks.
>>>
>>> 73's de KC4WVL
>>> William Smith
>>>       
>