Jim Here's my question: Why would one start playing with the temp setting of the inner oven first thing, on an old double oven unit that has not been on for 10 years. If it was because it was broken, it needs fixed, If it was to make it better, You would get much better results by Just letting it sit for a month or two INSTEAD of adjusting anything..What kind of poor TC was it existing over what WIDE temperature range that promoted you to play with the turn over temp setting. An more important, How could you tell it was TC error with the kind of initial aging drift you said it had? warren ******************* ----- Original Message ----- From: "Jim Palfreyman" <jim77742@gmail.com> To: "WarrenS" <warrensjmail-one@yahoo.com>; "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Thursday, August 06, 2009 3:24 PM Subject: Re: [time-nuts] HP 106B quartz frequency standard...the story so far > Hi All, > > Thanks very much for your interesting replies. > > I'm beginning to think I'm not letting it settle between adjustments. > And besides, The thing has been powered off for at least a decade I > would suspect and maybe I'm just watching the crystal adjust to micro > changes in temperature as it warms up. It's been on for about 10 days > with only about 30 min off time in between. I shall leave it on the > bench for a month or two before changing anything again. > > Now my next question is to those with double oven experience. The > service manual says the oven is "not field repairable". And there is > minimal description on how to get the oven settings right. > > The container has 61.3 C on the side - obviously the point of > inflection for the temperature curve of the crystal. There are two > test points which connect to either side of a thermistor buried deep > inside the inner oven. The label next to it say 432 ohms. The > resistance it should be at the correct temperature. I'm currently > running at 422 ohms (hotter) - that's the temperature that causes > minimal drift in frequency (at the moment - maybe this will change > after further burning in). > > The outer oven has no such thermistor. How do I know that is set > correctly? If it is too high, I'd assume it would heat the inner oven > too much and not allow you to drop the temperature in the inner oven. > If it is too low I'd guess the inner heater would have to use more > power and do more work to keep it ok. What is the ideal outer oven > temperature and how is this worked out? > > In all this, keep in mind my power rails are running a few volts high > and I'm not sure the effect this is having in the oven. > > Regards, > > Jim Palfreyman

Bob Camp wrote: > Hi > > Regardless of weather it's a single or double oven, you want the crystal > to be at it's "turn temperature". If you have a BT cut crystal, that's > going to be the highest frequency you find as you move the oven around. > With either a double or single oven, you should be able to "map out" a > parabolic plot of frequency versus temperature. That's only close to > "right" since the electronics contribute something to the temperature > performance. To really get it *right* you need to vary the external > temperature and see what happens .... > > On a double oven, the outer oven is set for some "nominal" amount of > inner oven current. The idea is to keep the inner oven controller from > either cutting off or saturating as the external temperature is varied. > Often the inner oven is set to the "low side" of it's power range. The outer oven can't have a too high temperature, since then the inner oven can't remove excess heat through conduction and reduction of heating power and you want sufficient balance between conduction and heating so that it does not cut-off since that way it becomes unregulated and loss of thermal gain is achieved. In a similar sense, too low outer oven temperature will saturate the heating power and again loss of thermal gain. The exact temperature of the outer oven is not that important as long as it provides the thermal gain and is within some temperature range that allows the inner oven to function properly. There is no magic to it, just some physics and control laws in action. Cheers, Magnus

Bob Mostly True, But I'd be willing to bet there are few out there that can tell or measure the difference between the factory setting and the 'best' Inner oven temp setting, Especially in a relative constant Lab environment. Unless they really know what you are doing and have the equipment & have a real goal in mind, best to leave it alone. If it is not broken , DON'T break it. warren *************** ----- Original Message ----- From: "Bob Camp" <lists@cq.nu> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Cc: "WarrenS" <warrensjmail-one@yahoo.com> Sent: Thursday, August 06, 2009 3:45 PM Subject: Re: [time-nuts] HP 106B quartz frequency standard...the story so far > Hi > > Regardless of weather it's a single or double oven, you want the > crystal to be at it's "turn temperature". If you have a BT cut > crystal, that's going to be the highest frequency you find as you move > the oven around. With either a double or single oven, you should be > able to "map out" a parabolic plot of frequency versus temperature. > That's only close to "right" since the electronics contribute > something to the temperature performance. To really get it *right* you > need to vary the external temperature and see what happens .... > > On a double oven, the outer oven is set for some "nominal" amount of > inner oven current. The idea is to keep the inner oven controller from > either cutting off or saturating as the external temperature is > varied. Often the inner oven is set to the "low side" of it's power > range. > > Bob > > On Aug 6, 2009, at 6:24 PM, Jim Palfreyman wrote: > >> Hi All, >> >> Thanks very much for your interesting replies. >> >> I'm beginning to think I'm not letting it settle between adjustments. >> And besides, The thing has been powered off for at least a decade I >> would suspect and maybe I'm just watching the crystal adjust to micro >> changes in temperature as it warms up. It's been on for about 10 days >> with only about 30 min off time in between. I shall leave it on the >> bench for a month or two before changing anything again. >> >> Now my next question is to those with double oven experience. The >> service manual says the oven is "not field repairable". And there is >> minimal description on how to get the oven settings right. >> >> The container has 61.3 C on the side - obviously the point of >> inflection for the temperature curve of the crystal. There are two >> test points which connect to either side of a thermistor buried deep >> inside the inner oven. The label next to it say 432 ohms. The >> resistance it should be at the correct temperature. I'm currently >> running at 422 ohms (hotter) - that's the temperature that causes >> minimal drift in frequency (at the moment - maybe this will change >> after further burning in). >> >> The outer oven has no such thermistor. How do I know that is set >> correctly? If it is too high, I'd assume it would heat the inner oven >> too much and not allow you to drop the temperature in the inner oven. >> If it is too low I'd guess the inner heater would have to use more >> power and do more work to keep it ok. What is the ideal outer oven >> temperature and how is this worked out? >> >> In all this, keep in mind my power rails are running a few volts high >> and I'm not sure the effect this is having in the oven. >> >> Regards, >> >> Jim Palfreyman >> >> _______________________________________________ >> 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. >> >

I'c curious, what is so strange about the pass xistor in the PSU that you can't replace it? -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Jim Palfreyman Sent: 06 August 2009 23:25 To: WarrenS; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 106B quartz frequency standard...the story so far Hi All, <snip> In all this, keep in mind my power rails are running a few volts high and I'm not sure the effect this is having in the oven. Regards, Jim Palfreyman _______________________________________________ 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.

2009/8/7 David C. Partridge <david.partridge@dsl.pipex.com>: > I'c curious, what is so strange about the pass xistor in the PSU that you > can't replace it? Getting one. So far I've found places with $300 minimum buys. However, as I write I can get one for $30 including postage to Australia. Still expensive. Unless anyone has a 2N1701 lying around? Regards, Jim

I meant with something not original that meets the specification ... Surely the specification can't be that extreme? D. -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Jim Palfreyman Sent: 08 August 2009 09:53 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP 106B quartz frequency standard...the story so far 2009/8/7 David C. Partridge <david.partridge@dsl.pipex.com>: > I'c curious, what is so strange about the pass xistor in the PSU that > you can't replace it? Getting one. So far I've found places with $300 minimum buys. However, as I write I can get one for $30 including postage to Australia. Still expensive. Unless anyone has a 2N1701 lying around? Regards, Jim _______________________________________________ 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.

Jim, I have a few old Fairchild transistors that would drop right in. They are AY9139 60V 4A Beta ~50 PNP Si. Much the same as 2N1701. Let me know and I'll pop some i the post. Max VK3YBA ----- Original Message ----- From: "Jim Palfreyman" <jim77742@gmail.com> To: "Discussion of precise time and frequency measurement" <time-nuts@febo.com> Sent: Saturday, 08 August, 2009 6:52 PM Subject: Re: [time-nuts] HP 106B quartz frequency standard...the story so far > 2009/8/7 David C. Partridge <david.partridge@dsl.pipex.com>: >> I'c curious, what is so strange about the pass xistor in the PSU that you >> can't replace it? > > Getting one. > > So far I've found places with $300 minimum buys. > > However, as I write I can get one for $30 including postage to > Australia. Still expensive. > > Unless anyone has a 2N1701 lying around? > > Regards, > > Jim > > _______________________________________________ > 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.