I have a 2110, not A or B or C, just 2110.  I've seen this same 'hunting' behaviour when measuring the 2110 against my 5065A.  It wasn't an oven fault in the 1150.  It turned out to be the beat frequency between the two oscillators.  This suggests some crosstalk in the measurement system, but it only appeared with the 2110, never with any other oscillator.  Adding a balun to the output of the 2110 reduced, but didn't eliminate the interference.  Retuning the 2110 to eliminate the frequency offset did eliminate the problem. Stewart, you mentioned a manual. Is it for the 2110 (not A, B, or C)?  I've never managed to track down one for my 2110. Ed On 1/12/2025 2:30 AM, Stewart Cobb <stewart.cobb@gmail.com> wrote: > From: Stewart Cobb <stewart.cobb@gmail.com> > Subject: [time-nuts] Austron 1150 OCXO advice? > To: Discussion of precise time and frequency measurement > <time-nuts@lists.febo.com> > Message-ID: > <CAPXiX5raqmbnu_w8Ueo6Apjhn1n+q=4cYS-+BSKid8n3Qb4_dQ@mail.gmail.com> > Content-Type: text/plain; charset="UTF-8" > > I have revived an Austron 2110 disciplined oscillator. This consists of an > Austron 1150 high-end double oven OCXO and a computer to lock it to an > incoming reference frequency and do some statistics and drift prediction. > It mostly works, but -- > > After a week of warmup, the OCXO is still about 25 ppb low, which is > outside the locking range of about 15 ppb. The OCXO has a mechanical > coarse > tuning adjustment, which the manual says to use in this case, but -- > > When I look at the main output with a TinyPFA (thanks, Erik Kaashoek!) and > TimeLab (thanks, John Miles!), its phase traces out a beautiful sine wave > with a period of just under 8 seconds and an amplitude of about 0.42 ns > p-p. The ADEV measurement shows corresponding ripples in an otherwise > stable trace. > > My interpretation of this data is that one of the two oven controllers has > gone wonky and increased its gain to the point that it's now unstable. > This > might well be due to the failure of an electrolytic capacitor in an > integrator loop. > > The manual refers to the 1150 as a "sealed unit" which must be returned to > the factory for repair. After 40-odd years and 5 or 6 changes of corporate > control (Sulzer? -> Austron -> Datum -> Symmetricom -> MicroSemi -> > MicroChip), factory repair is no longer possible, so I need advice > from the > group ... > > Is oven controller failure a reasonable diagnosis? > > Does anyone have documentation on the 1150 oscillator? (There is a > datasheet on KO4BB, but it describes a slightly different version. And I > have the pinout from the 2110 manual. In places, the documentation refers > to the 1150 as a Sulzer oscillator, so TVB's references a few days ago > might also be useful. But is there anything else?) > > Has anyone repaired a 1150, or even taken one apart? Are there photos of a > teardown anywhere? > > Does anyone have advice on how to open a "sealed" OCXO > nondestructively? Or > any other relevant comments? > > Cheers! > --Stu