[Elecraft] [K2] PLL reference test failure

[Don Wilhelm]

Ilya,

I am sorry you are having problems with the PLL Reference Oscillator. 
Yes, there have been several reports of this same failure.

First try a small value capacitor (10 to 15pF) from the source of Q19 to 
ground.

If that does not correct it, can you obtain a J310 FET locally?  If so, 
replace Q19 with it.

The problem seems to be that the J310 FETs in thru-hole format are fast 
disappearing from the market, and the last batch purchased by Elecraft 
does not operate well at the high frequency end of the PLL Reference 
Oscillator.
I am currently testing the J309 as a possible replacement.  The testing 
should be completed in the next few days.

One ham with a similar problem wired an SMD J310 on the bottom of the 
board with good results - if you cannot find a thru-hole J310, you might 
consider that solution.

73,
Don W3FPR

On 8/27/2018 4:47 AM, Ilya wrote:
> Hi Gentlemen!
> 
> I'm in progress of assembling my first K2 #7837 and now I'm stuck with PLL
> reference oscillator test. Seems that I've already read all previous email
> threads regarding similar problems all over the internet - and nothing
> helped.
> 
> When I just turn on my K2 after some time it's been off - I'm getting the
> following figures in PLL reference test (TP3):
> - Band + is 12099.1 khz
> - Band - is 12086.15 khz
> 
> After some time (just a minute or so), the BAND+ value starts drifting
> down. Drifting slows down with time, but in 2-3 minutes I'm getting 12070
> or smth like that. If I touch RIT/XIT knob - the value drops even lower -
> to 12055 or about that.
>