[Elecraft] K2 PLL reference oscillator problems (DAC side!)

[Don Wilhelm]

Chris and all,

Let me try to add some clarity to this J310 situation:

1. Thru-hole J310s have been discontinued.  Last August, Elecraft 
ordered a new supply (from a new source) which proved to be inadequate 
for the K2 PLL Reference Oscillator circuit.  A source of New Old Stock 
for J310s was sought and finally found.  Those parts were received in 
January 2019 and the stock that was deficient was scrapped.
2. So the K2s which were affected were shipped between mid-August 2018 
and January 2019.
Not all J310s shipped during that period were sub-par, some worked fine 
while others did not.

3. So this problem reared its ugly head on some of the K2s shipped 
during that period while others worked fine.

The problem would show up during the PLL Reference Range Test during 
early testing of the K2.  Many have been corrected so far, actually I 
hope all those which failed have now been corrected - time will tell.
With the current stock of J310s at Elecraft, this problem has been 
solved.  Warranty support for those K2s exhibiting the problem will be 
addressed as the symptoms are revealed.

The circuit is not to blame.  The circuit has been unchanged since the 
Field Test K3s and it has worked successfully until this J310 situation 
came up.

There are no new thru-hole J310s being manufactured from the original 
manufacturers - SMD J310s have no problems.

73,
Don W3FPR

On 5/29/2019 4:56 AM, Chris Smith wrote:
> Hi,
> 
> I have replaced the J310 and the oscillator now runs over the full voltage range of the DAC. Many thanks. After this, the PLL calibration routine completes successfully. The EEPROM appears to be ok here.
> 
> So at a high level the issue appears to be:
> 
> 1. The J310 or circuit was at fault. Either the J310 device spread is suspect or the circuit is device spread sensitive. Having built a few VXOs over the years some problems are almost inevitable here so it's expected really.