Hi All I just finished assembling my K1 transmitter, and managed to make a first QSO with it (France -> Bulgaria). Everything was OK, except that the frequency was sometimes very unstable. I suspected some cold solder or missing component, since I noticed that the RIT was also not working (even if the LEDs were showing RIT and XIT modes). I opened the covers, connected an oscilloscope to the OFFSET signal, and found it always at 0 volts. Then I searched for eventual short circuit, or cut wire. The thing is that when I touched the RIT potentiometer axis, the OFFSET voltage suddenly raised to 2 to 3 Volts. I suspected a faulty potentiometer, with poor wiper pressure, but the resistance measurement was correct. Finally, the reason was an intermittent short circuit between the Potentiometer metal body (4 x sharp legs) sitting right on PCB traces underneath (one of them being the OFFSET signal...) the green solder mask not offering a sufficient insulation. Immediately, I de-soldered the RIT potentiometer, cleaned the flux residues, and pasted a 1 square centimeter piece of scotch tape on the PCB surface, before replacing the part. Since then, the K1 does not suffer anymore of intermittent instability! If this message could be of some help for other builders, or for a new PCB design version... Vy 73 from Joseph / F6ICS QTH near PARIS
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