Yes - Matt is correct - I forgot to advise about the warm up time - also there is o real problem about the battery - plan on replacing it but it will not cause YTO unlock.
Cheers!
Bruce
Quoting Matt Huszagh <huszaghmatt@...>:
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To add to Bruce's answer: the REF unlock can occur when the OCXO oven is
warming up. If the unit has been plugged in (doesn't need to be powered
on, since the oven supply is active anytime the instrument is connected
to mains) more than ~10min or so and the annunciator is still there,
that's an indication there's an issue. FYI although the oven supply is
always present when plugged in, the oscillator supply isn't. You'll need
to power on the unit to see the 10 MHz signal.
I would start by just checking to make sure this 10 MHz signal is
present. You don't need to open the instrument, it's available on the
back panel. Any oscilloscope should be able to tell you whether the
reference signal is present or not. I got a ref unlock on an 8340 (same
reference as the 8566) and it was caused by a dead reference.
If the reference is dead, you can test the rest of the instrument by
providing an external 10 MHz reference. Check the manual to ensure the
power level is appropriate. If you're not getting a 10 MHz signal,
before ultimately implicating the reference, you should ensure all
interface signals to the reference (including both the oven and
oscillator supplies) are correct.
If the reference is present but you still see the REF unlock that will
require some additional troubleshooting.
Good luck,
Matt
