Robert, The drift has slowed down to something around 8xE-10, which is a bit over the spec of <5E-10. But this is the single oven, I have not reassembled the double oven yet.
If the oven regulation was off, I would suspect I would see the EFC go back and forth a bit, maybe a general trend up, but some retracing would be expected. The oven control is an integrator, so unless the offset is very large compare to the output of the thermistor, a continuously changing offset voltage will not have a large effect on setpoint. A crystal resonator will drift about 1-5E-8/degC, so I guess a loose temperature control would certainly exhibit the drift I am seeing. Bob >>> -----Original Message----- >>> From: time-nuts [mailto:[email protected]] On Behalf Of George >>> Atkinson >>> Sent: Monday, September 14, 2015 2:42 PM >>> To: Discussion of precise time and frequency measurement >>> Subject: Re: [time-nuts] Z380XA The saga of the aging 10811 >>> >>> Well, if the batch/revision of op-amps had a doping, contamination or similar >>> issue, the input offset could be drifting fairly constantly causing a >>> temperature channge in one direction. >>> >>> Robert G8RPI. >>> >>> On 9 September 2015 at 04:40, Bob Benward <[email protected]> >>> wrote: >>> >>> > Hi Ed, >>> > OK, a bad oven. I can buy that. But then if the oscillator is >>> > constantly drifting, would that not imply that the oven is constantly >>> > changing temperature, in one direction? >>> > >>> > BTW, the curve is starting to flatten out. It might be flat before It >>> > gets to 1000K counts. >>> > >>> > Bob >>> > >>> > >>> -----Original Message----- >>> > >>> From: time-nuts [mailto:[email protected]] On Behalf Of >>> > >>> ed breya >>> > >>> Sent: Tuesday, September 08, 2015 10:55 AM >>> > >>> To: [email protected] >>> > >>> Subject: Re: [time-nuts] Z380XA The saga of the aging 10811 >>> > >>> >>> > >>> It could be that the inner oven temperature regulation is off a >>> > >>> bit, or >>> > even >>> > >>> failed. There was a report at one of the popular time-nuts >>> > >>> oriented >>> > websites (I >>> > >>> forget which one, but it's the one that had extensive coverage of >>> > >>> the >>> > Z3801A) >>> > >>> about inner oven problems a few years ago. I took mine apart and >>> > >>> found >>> > that >>> > >>> it had an IC of a particular date code range that was prone to failure. >>> > I can't >>> > >>> recall whether I replaced it with the same type but different >>> > >>> date, or >>> > an >>> > >>> alternative, but it worked just fine after that, with no tweaking >>> > >>> of >>> > coarse EFC >>> > >>> needed. >>> > >>> >>> > >>> The IC was a dual opamp I think, that controlled the oven >>> > >>> temperature according to the thermistor signal, and drove the heater >>> transistor(s). >>> > >>> It was a fairly high performance type, but not that unusual. I >>> > >>> think it >>> > was a >>> > >>> Linear Technology brand part. >>> > >>> >>> > >>> Ed >>> > >>> _______________________________________________ >>> > >>> time-nuts mailing list -- [email protected] To unsubscribe, go to >>> > >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> > >>> and follow the instructions there. >>> > >>> ----- >>> > >>> No virus found in this message. >>> > >>> Checked by AVG - www.avg.com >>> > >>> Version: 2015.0.6140 / Virus Database: 4409/10580 - Release Date: >>> > >>> 09/05/15 >>> > >>> > _______________________________________________ >>> > time-nuts mailing list -- [email protected] To unsubscribe, go to >>> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> > and follow the instructions there. >>> > >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> ----- >>> No virus found in this message. >>> Checked by AVG - www.avg.com >>> Version: 2015.0.6140 / Virus Database: 4419/10639 - Release Date: >>> 09/14/15 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
