[Elecraft] [K2] TX Issue in Part III checks

[Brian Handy]

Hi All,

I've been working on my K2 and I'm on the home stretch.  I had to dabble a bit 
to find a cold solder joint in the Part II checks, but eventually got a 
home-brewed test oscillator to reach through on 40m!  Quite happy with things so 
far, and learning a lot.

I still have a lot to learn about the transmitter side though, that doesn't 
work.  When I first hit 'tune' in the Part III checks, I noticed high current on 
the power supply, high current on the front panel, and changing the power level 
didn't help, it was always high draw.

It didn't take much of this to zorch the PA finals and short things straight to 
ground.  Nothing worked until I pulled T3, and while I had the soldering out I 
took out the PAs and started looking around and reading the mail archives.

I noted one suggestion from Don to someone else and checked the voltages on base 
on the finals - both are around 0.65V, which I think is OK.

I realize things won't be quite the same without the PAs there and proper 
feedback happening, but ... I then started going through all the voltages on the 
RF board with TUNE on.  Everything looked pretty much fine except for Q24 ~

Leg - Expected - Measured:
G    - 0V - 5.6V
S - 1.2 - 2.5V
D - 13V - 0V

That doesn't look right at all to me.  Exploring further, I started chasing VALC 
down the rabbit hole.

Pin 2 of U8 (V PWR) seems to vary between 3.8-5V as I turn the PWR knob in 
TUNE.  I decided that was OK.

Pin 1 of U10A doesn't move around a lot, only up and down about 0.1V.  Finally 
the emitter of Q8 (V ALC) seems stuck at 7.4V.

I was firmly confused at this point, so went back and started checking Control 
Board voltages per the page of expected readings in the back of the manual with 
CAL FCTR turned on.  Everything seems turned off when I do that and I'm seeing 
pretty much 0V everywhere.

I'm a bit saturated at the moment, but thought I would ask if this sounds like 
I'm on the right track, or if I have to get to poking elsewhere ... 



Cheers and thanks in advance,

Brian Handy
AE7JW
Tokyo, Japan