[Elecraft] PLL problems with K2 #5061

[M. P. Haynes]

Hello folks,

I think I must be kin to Joe Bftsplk of L'il Abner fame years ago.....I
seem to have a black cloud hovering over me as I build and check #5061. 
I had a problem with Q6 being overtaxed by a 4V bias on the base during
keydown which turned out to be a shorted Q10 FET.  When I got that fixed
I anxiously started to finish the calibration only to find the PLL now
won't lock!  I had that problem during the build which turned out to be a
solder bridge on the thermister board shorting the 4V ref for the PLL
comparator.  Once I fixed that the cal went smoothly.  

I have rechecked all connections on T5 and have reheated all connections
on the RF board with no improvement.  The oscillators are running (I can
hear stations drift by as I put my finger near T5 or other oscillator
components or when I tweak L30.)  I have scoped all signals in the PLL
chain and they are all there except for SCK.  I checked that signal on
the control board and it is also missing.  The signal sits at logic high
with no pulses.  I would expect that signal to run all the time if I
understand the circuit correctly.  I removed the control board and
reseated U6 MCU with no change in symptoms. 

Anyone have any suggestions where to go from here?

Thanks in advance,

Pat Haynes-K4BEH
(706) 692-0279