[Elecraft] KNB2

[Don Wilhelm]

David,

To test, turn on the preamp and tap Q21 with a screwdriver tip - you can 
tell when the sharp 'clicking' with each tap is taken out by the KNB2.

There is not a lot of circuitry on the KNB2, so I suggest that you check 
all the components for correct values, and in the right positions.  Make 
certain the diodes are oriented in the correct direction.

Look at the schematic and identify the voltages that will be present for 
the 2 thresholds (U3 pin 6) and the two pulse widths (U3 pin 7).  If you 
have a logic probe or better yet a 'scope, you should be able to see if 
the one-shot is producing gate pulses (collector of Q4).

Remember the most common cause of problems is the soldering followed by 
poorly tinned toroid leads and misplaced components - check these 
carefully as your first efforts, try to look at it critically as though 
someone else had built it.

73,
Don W3FPR

David N. wrote:
> Ok I have gone over my KNB2 Board twice now to see why
> it will not blank any noise. I had a friend of mine
> come over here with his and we used my noise source. 
> (1948 Ferguson Tractor) Noisy ignition. He set his for
> nb1 and badda bing badda boom all gone mine still
> there. NB2 Still there. I asked hime if he did
> anything to his and He said nope just the way it came.
> 
> I did research through the archives and found a note
> about scratching the surface of Q22 But that is not
> possible on mine it is under the NB2 Board. So What
> can I do to troubleshoot mine.
> Thanks
> David KR4OW
> K2 4320
> 
> 
>        
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