Hi all, I'm still relatively new in this area but I'm trying to troubleshoot an issue with a Datum 1000B I picked up last year. This unit is the 10MHz flavor with 4 outputs. Its issues, I believe, is after 24 hours of warm-up, the oscillator: - ...has a flat-out dead output for one of the outputs, other 3 outputs work - ...exhibits an unstable frequency output, from all working ports
I own only a modest set of equipment (Racal 1992 and a Thunderbolt I bought from the group-buy years ago) for frequency testing, but my Racal is showing me the frequency is fluctuating between just under and over 10MHz. Someone on this list previously coined the term "poor-man's spectrum analyzer" method with a Thunderbolt, and that's what I did - I stuck the oscillator output to my modified external-oscillator fed Thunderbolt. This Thunderbolt has been used to discipline a variety of oscillators (10811A/D and 60111s, Morion 89A) and generally shows 30-50ppt with the noisy GPS reference. With the 1000B it's showing about a 500-1000ppt fluctuation with GPS. While I know GPS is generally noisy, I'm pretty sure the 1000B figure isn't normal. My test setup is +24V connected to all powered inputs and the EFC input is grounded. The trim pot on the oscillator face does seem to be able put the oscillator on-frequency. I'm hoping this list can tell me what common issues this old-ish unit generally exhibits in terms of instability before I deep dive into its innards, but here are my thoughts: - Large 24V supply ripples - Bad oscillator power regulator(?) - Failed oven heater controller to heat crystal to its turn-over point? I don't think it's any of the output buffer circuits since this noise appears on all working outputs... The unit starts up with a current consumption of 410mA cold, then drops to about 80mA @ 24V after fully warmed up. Any suggestions/pointers from this list would be welcome! -Eugene _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.