[Elecraft] [K3] Disappearing VCO error

[Ian White GM3SEK]

Yesterday morning, I wrote:
>
>After the K3 had been running for a few hours yesterday evening, just
>listening to the bands, it stopped working with ERR PL1 (and PL2). These
>were genuine hardware errors - neither of the two VFOs would tune and
>both receivers were dead. Attempts to re-calibrate the VCOs ended with
>ERR VCO and ERR VC4.
>
>I switched off and left the problem overnight, and this morning both
>VCOs calibrated successfully with no further errors so far.  (A notable
>difference was the successful calibrations took much longer over some of
>the steps. The failed attempts had rattled through all the steps at the
>same high speed.)
>
>The firmware was MCU 4.12 / DSP 2.60 / FPF 1.13.  After everything was
>working correctly again, I have updated to MCU 4.14.
>
>Hardware is K3/100 #724, with KAT3, KRX3, KXV3 and all modifications to
>date.
>
>The question is: why did this happen? And with CQWW SSB coming up, could
>it happen again?
>

By 10am Aptos time, answers from Elecraft were in my inbox!

Dale confirmed that the faults as described were almost certainly due to 
loss of signal from the 48MHz reference oscillator on the KREF3 board. 
Since I had been doing some unrelated mods that required the removal and 
replacement of the KRX3 (several times over) it is very possible that 
the oscillator module had been knocked, and that contact in the socket 
had become marginal.

Eric added that the Clock to Data timing on the internal serial bus is 
critical to proper operation, and that recent firmware releases include 
an additional timing margin.

On opening up the K3 again, there wasn't any obvious problem with the 
seating of the oscillator module, but I removed and re-inserted it 
anyway. Instead of the single tie-wrap that was provided in the kit to 
secure the module in its socket, I tried using two slightly thinner ones 
which ensure that the module is pulled firmly downward at *both* ends of 
the package.

Grateful thanks to Dale and Eric for such a rapid and accurate response!

Cross fingers for the weekend... and good luck in the contest to all K3 
users.


-- 

73 from Ian GM3SEK / GM3Whisky
http://www.ifwtech.co.uk/g3sek