[time-nuts] Z3801A EFC Error

[Ed Palmer]

I don't think I would call the coarse tuning adjustment 'accessible', 
but it does exist.

http://www.realhamradio.com/GPS-oven-journey.htm

Of course, before digging into a mess like that, check the standard 
things like power supply voltages, outer heater current draw, bad solder 
joints that got shaken up during the move, etc.  Maybe the unit took a 
jolt during the move and the crystal just needs time to settle down.

Ed

On 7/10/2011 8:38 AM, John Ackermann N8UR wrote:
> 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
>