[time-nuts] HP 106B quartz frequency standard...the story so far

WarrenS warrensjmail-one at yahoo.com
Thu Aug 6 22:55:08 UTC 2009


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 at gmail.com>
To: "WarrenS" <warrensjmail-one at yahoo.com>; "Discussion of precise time and frequency measurement" <time-nuts at 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



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