[time-nuts] Z3801A EFC Error

[John Ackermann N8UR]

I'm getting my two trusty Z3801As up and running after 18 months of 
downtime and a 500 mile move.  Unit #1 came up just fine.

Unit #2 has been running for about 18 hours and is working OK except 
that the health status is showing an EFC error.  The EFC value is above 
1e6 (currently 1014166) and is trending downward, though the trend has 
leveled off in the last several hours.  I suspect that the health 
monitor error comes on to indicate that EFC is near the end of its 
range; if I query for relative EFC, it comes up at about 93% so perhaps 
the trigger is 90%.

Other than the EFC error in the health monitor, the unit seems to be 
working fine.  LEDs show normal activity, the Oven PWR and OCXO health 
status are both OK, and after initial alignment the PPS seems to be 
holding within a handful of nanoseconds.  (I'm using GPSCON for tracking.)

It's possible that the EFC could keep trending downward as the unit 
stabilizes, and if that continues to be the direction there should be no 
problem.  But if it starts to go up, I'll run out of tuning room soon. 
Assuming there's no other hardware problem, I'd think the normal way to 
address this would be to twiddle the oscillator's coarse frequency 
trimmer to get it centered in the tuning range.

Before I tear into the box, is there a coarse frequency adjustment 
accessible on the dual-oven 10811?  If that's not an option, any other 
suggestions on what might be going wrong and how to cure it?

John