[Elecraft] [K1] [KNB1] Noise blanker not detected (three dashes ---)

[Bogdan - Constantin Lazanu]

Hello,

This is my first message to this mailing list, so please be gentle!

During the summer and autumn I built my first ever kit: the K1-2 (#3449) + KAT1. Everything worked surprisingly well (being a first-timer and all), I never had any problems. Until now. It seems that I failed in my “build-without-help” venture :)

A few days ago I completed building the KNB1 option and when I got to the “Initial Test” phase I noticed that in the menu, instead of HI/LO/OFF I can only see three dashes (---). The instructions say that the K1 firmware has not detected the noise blanker module and that a possible cause may be that the U3 was soldered in backwards. I assume that’s a mistake - there is no U3. Just a U1, and it’s soldered properly.

Some details:

- The K1 firmware is revision 109
- The KNB1 PCB is revision Cr
- U1 on KNB1 has a small paper label with “NB 1.02” written on it
- Turning the trimmer C2 on KNB1 does vary the band noise and received signal strength
- There is continuity from KNB1 U1 pins 3/4 to the front panel U1 pin 8 (6R/AUX) - around 182 ohms
- The voltage between KNB1 U1 pin 1 (VDD) and GND is 6.03V
- The voltage between KNB1 U1 pin 5 and GND is 5.59V (this is the 6V switch for the noise blanker)

That’s about as much information as I can think of right now.

Has anyone else encountered the same issue before? At the moment I’m thinking that KNB1 U1 may be defective, but I don’t know how to make sure. I would appreciate some assistance in solving this.

Many thanks for taking the time to read this message!

73,
Bogdan YO8SAW