[Elecraft] Problem with KAT2 Bridge Null Adjustment

[Dauer, Edward]

Thanks, Don.  I did check that, and redid all of T1’s solder joints.  No 
change.  I was about to rewind T1 altogether when I decided to check the 
archives.  Using a search method earlier suggested by Phil, W7OX, I found 
a post by you in 2013 answering the very same question.  On reading it 
something struck me — the person posing the question recited that he had 
set the process up by, among other things, turning both R1 and R2 fully 
clockwise.  That hit me — I had read that instruction as full COUNTER 
clockwise!  I checked the manual again, and there it was - full clockwise. 
 So, after doing that the right way, and suffering some chagrin, all was 
good.  The U4 pin 1 voltage is a bit low at 2.8, but the null voltage gets 
down to 006 using C55 as prescribed.

What you just wrote would have been exactly right - if I hadn’t been so 
d*****d stupid.  Thank you for not thinking that I could have been.  

“RTFM” is now amended to read “RTFM-C” where C = carefully.

I am posting this on the reflector by way of self-discipline.  If I didn’t 
confess it publicly, I’d be less likely to learn from it.

Thanks, as always.

Ted, KN1CBR






On 5/7/16, 12:24 PM, "Don Wilhelm" <donwilh at embarqmail.com> wrote:

>Ted,
>
>You will find the problem is with T1.  It must be wound and installed 
>exactly as shown in the manual, and that includes the direction of the 
>winding.
>
>Your K2 is likely putting out all the power it is capable of, so do 
>those TUNEs for only a short period or you will be replacing the PA 
>transistors.
>
>73,
>Don W3FPR
>
>On 5/7/2016 12:02 PM, Dauer, Edward wrote:
>> Advice requested for the following problem:
>>
>> Completed and installed the KIO2.  That works fine, so far as it has 
>>been tested with the outboard ("twins") KPA100 and KAT100.  Next step 
>>was to put the amp and high power tuner aside and install a KAT2 in the 
>>base K2.  [In case it matters, the K2 does not have the battery option.]
>>
>> All went well with the KAT2 until the Bridge Null Adjustment.  There 
>>are two strange symptoms:
>>
>> First, adjusting C55 has no effect, and the display does not behave as 
>>it should.  When Tune is held, the display first says HiCur, then it 
>>quickly changes to ATU and then, again quickly, it changes to 000 and 
>>stays there.  Adjusting C55 to every possible position changes nothing.  
>>Each try produces the same display:  about 2 seconds of HiCur, two 
>>seconds of ATU and then 000.
>>
>> Second, the DC voltage at pin 1 of U4 is way off.  In Receive Mode it 
>>reads 0.0, as it should.  But in Tune mode, at 5 watts indicated, it 
>>reads only 0.69 DCV rather than the 3.0 to 4.0 expected.
>>
>> I haven't put an external power meter on the rig yet but a 15-watt 
>>dummy load gets warm after a while so there does seem to be RF output.
>>
>> I see no solder bridges, no cold joints, no breaks or shorts thatI can 
>>see.  The plugs and sockets have been checked at least five times to 
>>assure they are properly aligned and properly assigned.
>>
>> Any ideas, anyone?  Thanks!
>>
>> Ted, KN1CBR
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>