Yes you should see the pulse there. I had the same problem when I built
mine a few years back and ended up right where you are, but what I found was
that I had a bad connection on C8 the coupling cap on the output of Q5. The
result will also look like a bad Transistor with no pulse showing on the
collector.
Good hunting.
Gregg R. Lengling, W9DHI, Un-Retired
K2/100 SN 3075
http://www.milwaukeehdtv.org----- Original Message -----
From: <
[hidden email]>
To: <
[hidden email]>
Sent: Tuesday, November 15, 2005 8:36 AM
Subject: [Elecraft] KNB2 Noise Blanker Not Working
> I've had my K2 built for about 2 months now. Everything works except the
> noise blanker. I've looked at a lot of archives on this. What I have
> done to test it is:
>
> 1. Scratch the top of Q21 on the RF board to generate noise.
> 2. Using an oscilloscope, I can trace the noise pulse through Q2-Q4 on
> KNB2 borad.
> 3. I do see a noise pulses on the "GATE" node and at the base of Q5.
> When I turn off the NB, this pulse goes away as expected.
> 4. I do not see any pulse on collector of Q5. Since the pulse on the
> base of Q5 saturates Q5, should I see anything on the collector?
>
> I'm not sure if I have a bad Q5. I am going to replace it today.
>
> Thanks,
> Leon, NE0N
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