[time-nuts] Caring for the elderly (OCXO)

Bob Stewart bob at evoria.net
Sat Aug 31 17:48:46 UTC 2013


My OCXO is a Trimble 34310-T that I bought from a China recycler a month or so ago.  It has been very stable until this morning.  At about 10:30AM my PLL showed a large blip during one segment  count (1PPS) and the DAC started tracking upward to stabilize.  Then, 745 seconds later it glitched in two successive segments and the PLL has tracked the DAC downward well below the old stable number.  For an independent reference, I have my 8640B self-locked inputting on Channel A of my 5335A with a large enough gate for 8 decimal points of display.  My GPSDO is serving as the time reference for the 5335A.  Give or take the stability of the 8640B, the counter seems to agree with what my GPSDO is doing.

This is for hobby and learning, so no big deal, but I'm wondering if this is how OCXOs start misbehaving in their dotage (so to speak).  On the one hand, it gives me another insight into error handling for my PLL logic, which is good.  But, on the other: I'm wondering if I should just give it a proper burial and put in my spare?  Maybe I'll leave it in to see if any other error modes develop, and then toss it when I finally have code I'm willing to share.  Anyway, is this oscillator on its last legs?  I'm more worried about letting out the magic smoke and damaging other components than I am about accuracy at this point.  

Bob - AE6RV


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