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
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