[Elecraft] K2 S/N 7012 lives!

[Alan Davenport]

K2 S/N 7012 lives!
 
I just finished assembly and testing of my K2 and it is working 100%.
 
It was a wild ride with many ups and downs. 
 
First down was at the very first checkout. The K2 refused to power up. There was 
a brief click the nothing. Fuse F1 got hot to the touch. I eventually tracked it 
down to a solder splash shorting 12v to ground on the control board. The first 
"up" was after I fixed that and it came to life for the first time.
 
The next down came at the second checkout phase. I had no signal at TP3. I found 
that I had wound T4 incorrectly. The was found and corrected easily.
 
The last and biggest down came at final checkout phase. I had ZERO transmitter 
output, no 80m recieve and weak 12m recieve. I figured I would fix the recieve 
first. I was doing signal injection to try to track down where 80m was failing 
when the clip lead slipped out of my hand, fell on the PA transistors and thus 
blowing them out! (Prior to this the resistance/voltage checks on them was 
fine.) Talk about a sinking feeling in the pit of ones stomach! I ordered 
replacements and while waiting for them to arrive I set myself again, much more 
carefully, to fix the 80 and 12m recieve. 80m turned out to be a poor solder 
connection and 12m turned out to be a damaged capacitor which I ordered and 
replaced. 

 
While waiting for the replacement PA transistors to arrive, I built and added 
the AF filter and the noise blanker modules without incident.
 
After the replacement PA transistors arrived I installed them ad STILL had 0 
transmitter output. Remembering the T4 issue, I rewound all the transformers in 
the PA circuit. Still no output. I tried tracking the problem down without 
success. I finally admitted defeat and got help from Elecraft support. They 
provided a check list to follow. Very shortly thereafter I found a solder blob 
shorting two leads on Q3 on the control board. After reassembly I was rewarded 
with power out on all bands. The best heat I ever felt was my 4W dummy load 
getting warm when I pressed "tune"!
 
Lessons learned:
 
Get a GOOD, temperature controlled soldering station BEFORE starting. I did the 
beginning part of the control board with a Weller 25W pencil iron but it had NO 
temperature control and after being on for more than 10 minutes or so was really 
too hot to use effectively. Remember, both my serious issues (With the exception 
of the OOPS!) were due to solder problems on the control board. A good soldering 
station is key. 

 
Be careful to wind the toroids EXACTLY as the manual states. Sand the leads 
until ALL you see is nice, shiney copper.
 
Pick up a GOOD pair of diagnal cutters. Mine wer a bit dull and made things 
difficult until I bought new ones.
 
A couple parts were initially installed in the wrong place. If you are getting 
tired, STOP. I made these mistakes when I worked too long. Take your time! Don't 
skim the instructions, read each word as if your life depended on it. hihi
 
Some parts are tiny. Get a good light and a good magnifying glass. I used and 
LED headlamp and a jewler's loup. Towards the end I was triple-verifying 
components before soldering.
 
The tiny capacitors are FRAGILE. Despite care on my part I DID damage one.
 
Last but not least was Elecraft technical support. They are the best and I could 
not have done this without their guidence. Thank you guys!
 
All-in-all it was a great experience. I look forward to many years of fun with 
the radio!
 
73 de Al, W2GZN.