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Mike, NI2S's Ham Blog

Page 12

 15-JAN-08: Automatic Antenna Tuner Build.  Control Board Assembly

    The Control Board is one of two PCB's that make up the Auto Antenna tuner.  This is another cramped board requiring some care, but it was not all that challenging.  The first page of installation went smoothly except for 1 capacitor.  I carelessly installed the wrong cap.  Luckily my check, double check, triple check approach saved the day, as I caught the error and corrected it.  No harm except to my pride.  Here is a pic of the board after Page 1 of instructions are complete:

I started assembling this board before I realized there was an errata page for the manual - which I (not so) smartly tucked into the back of the Ant. Tuner manual. Thus while thumbing through the manual looking ahead, I discovered the hidden Errata page.  To my dismay there was a note on the work I had already done concerning R6.  The Errata instructed not to install it, but of course I already had.  The wording of the Errata suggested R6 was to be installed later, but I couldn't find the note to install it, so I decided to email Elecraft and see if R6 was to be discarded.  Less than two hours later, here is what Gary Surrency of Elecraft tech support had to say:

"R6 is left out for preliminary testing to prevent damage to the K2 PA transistors, if there is a problem with the KAT2 SWR sensor FWD detector output. This would cause maximum RF output with no indication of this on the K2's front panel.  R6 later gets installed on page 17 of the KAT2 manual. Don't miss that step, and use care when first testing the atu."

 I didn't see the note on pg 17 about R6, so I am glad I asked.  R6 was removed and set aside without incident, and I continued on.

The next challenge for me was the winding and installation of T1.  This component required 2 wires twisted together and then wound around the core.  My problem was that one wire was colored red, the other green, and the resulting four leads had specific PCB pads assigned in a specific order...uh oh.  As mentioned at the beginning of this blog, I am color blind in red and green.  After contemplating this problem, I finally decided that the two colored wires had a sufficient enough shade difference that I could distinguish between the two without mixing them up.  I guessed at which was red, and which was green.  Here is a pic of the wound toroid.  Note the leads - there was plenty of excess on this winding chore.     I had no problem tinning the leads using the solder blob method.  Next I ever so carefully separated the two "red" and two "green" leads according to the Elecraft diagram, and after checking, and rechecking the orientation over and over, I soldered the component to the PCB.  I think I got it right. 

After that tense work, there were only a few parts left to install before the board was complete.  Here it is in all it's glory:

    Now time for the LC PCB of the Ant. Tune kit....