[time-nuts] Things I've learned about Odetics 325's

[Bruce Lane]

	Just some hints and tricks for others who may come to own Odetics 325 clocks.

	First and foremost: I have a collection of files, including the user's manual and EPROM image files for the last known version of firmware, available on my FTP site: ftp.bluefeathertech.com -- Anonymous logins only, no direct uploading permitted, limit of five users at any one time. Be sure to set your FTP client to access the site on port 50021 instead of the normal 21. This was done to discourage script kiddies from cluttering up my logs.

	Login as user 'ftp' (without the quotes). Use any password you want that contains printable characters, though I prefer you use your E-mail address (this for logging purposes). The path is /electronics/radio/GPS/clocks/Odetics.

	Keep in mind that the firmware I have is specific to Odetics clocks that have been retrofitted with the Magellan GPS receiver, and that the firmware change associated with that retrofit essentially turns the unit into a model 425. The firmware may not work for earlier models, but at least this is a way to replace an EPROM if one goes bad (and I have indeed seen them go bad).

	ON ADJUSTMENTS: I've found that the OCXO and associated circuitry in the 325 are very picky about correct adjustment (no big surprise). If the unit is not set correctly, you will get FLT indications along with things like "Time Coasting" on the readout, and your TFOM (Time Factor of Merit) number may never drop below 6 or higher (it should be 4 under normal conditions).

	The best possible way I've found to set the oscillator is to trigger the horizontal timebase of a good O-scope with the 10MHz output from another GPS, cesium, or rubidium clock, one that is known to be functional and accurate. Next, take the 10MHz output from the Odetics and pipe it into one of the vertical channels.

	Crank up the sweep speed until you have a clear sine wave. It will likely be moving across the screen towards one side or the other. Next, follow the instructions in the manual for setting the DAC number to its centerpoint.

	Once you've set the DAC, look on the backside of the 325 and remove the seal-screw that covers the coarse adjustment port of the OCXO. Stick a jeweler's screwdriver in there, and slowly tweak the trimpot you'll find (with a little maneuvering) until the 'scope display is holding perfectly still.

	Put the seal-screw back in, and follow the manual's procedure to restart the estimator. Let the thing sit about an hour or so. Assuming everything else is OK, you should end up with 'Time Locked' and 'TFOM = 4' in the display, and no 'FLT' indications. If it doesn't cooperate in this regard, try power-cycling the unit and give it another half-hour or so to lock on.

	If it still doesn't cooperate, you may have a bad OCXO, or a different problem.

	Happy tweaking.


-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"