[time-nuts] Z3801A failure?

[Bob Camp]

Hi

I would bet the OCXO is off frequency. Bad heater or some other basic failure. 

Bob


On Mar 28, 2010, at 6:57 PM, Matthew Kaufman wrote:

> I'm new to the list, but an occasional archive reader. I've built a homebrew GPS-locked simulcast UHF repeater system out of off-the-shelf parts, including doing all the audio phasing in software. The technical details are at http://www.wb6ece.org/ if anyone is interested.
> 
> I have a half-dozen sites, and I'm using Z3801A units for the 10 MHz to lock the transmitter PLL and the 1 PPS to synchronize the audio at all of them. So far, I've had two of the units exhibit the following failure mode:
> 
> The unit keeps operating and generating approximately 10 MHz, but it unlocks and drifts off, and the 1 PPS drifts way out of phase (not surprising, given its source), even though it is apparently still getting valid GPS info.
> 
> Power-cycling the unit doesn't restore it. One is still in this mode up on a mountaintop (that I intend to visit in the next week or two), the other is back on my workbench after a swap... I didn't see anything obvious on the system status page just before swapping it, but I was in a hurry to get the replacement in place. When I powered it up after a few months of sitting untouched, it came up seemingly ok but is now (after an hour or so) showing an EFC error, the EFC value is full negative, and the EFC voltage on the testpoint is -4.99 volts. The TI value is drifting slowly more negative. This is with good GPS info, though I am re-surveying as the initial location was 50+ miles away from here.
> 
> So: What should I be looking at next on the one that's on my workbench? What, if anything, should I try to extract from the one that's on the mountaintop when I get there? And what should I replace these with (if anything) that's also inexpensive, preferably easy to power (I mostly run these off of 12-to-48 inverters so they can use the 12v power bus I have for the radios), but less likely to require a drive to the mountaintop?
> 
> Matthew Kaufman
> 
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