[time-nuts] HP 10811 update

Bob Camp lists at rtty.us
Fri Jul 26 12:08:14 EDT 2013


Hi

HP spec'd the crystals to be at a < 1x10^-8 / C slope at the marked temperature on the crystal. The center of the curve should be in the vicinity of 90C. 

You are ~ -4.5 x 10^-6 low, so that would be > 10 C away from that point going cold and a bit further going hot. Since the oven is at ~80C, it's not to hot…

Bob


On Jul 26, 2013, at 10:09 AM, paul swed <paulswedb at gmail.com> wrote:

> Good comments. Indeed I will order up a new xtal from digi-key. They should
> be in stock any day now. I do agree with the comment on the cap in
> parallel. I had not thought about the series cap dropping and there is a
> .1uf as I recall. Need to look. The varicap seems to work very well so
> don't believe thats an issue.
> Will do some more hunting.
> By the way as a heads up the top and bottom cover of the xtal compartment
> are actually a pain to screw back together.
> Anyone have a sense of the Hz change per degree C?
> Thanks
> 
> 
> On Fri, Jul 26, 2013 at 8:52 AM, Bob Camp <lists at rtty.us> wrote:
> 
>> Hi
>> 
>> Ok, since it's moved *down*  and it's about on temperature there are a
>> couple of likely possibilities:
>> 
>> 1) The crystal leaks and there's air in it
>> 2) The trap coil(s) / capacitor(s) have changed value
>> 3) The varicap is shorted / forward biased
>> 
>> Normal factory troubleshoot (after checking the varicap) would be to swap
>> the crystal and see if the problem follows the crystal or the oscillator.
>> Yes, I know, that's not very helpful in this case - sorry about that.
>> 
>> Bob
>> 
>> On Jul 25, 2013, at 9:32 PM, paul swed <paulswedb at gmail.com> wrote:
>> 
>>> Well lucks not so good do have the voltage closer but as Bob C said. That
>>> ain't the issue.
>>> Darn I hate when he is right. By the way the oscillator draws 26 ma
>> approx
>>> as a reference. Reassembled everything and let the oven heat up it
>> settles
>>> at 81C 15 min after start and within a respectable range of the temps
>>> listed in the service manual. Measured with a K thermocouple. Freq is at
>>> 9.999955. or 45 Hz low
>>> Tuning the variable cap has 20 Hz range and the cap was pretty much
>> center
>>> range. Have not played with the varicap but that should have a very small
>>> effect.
>>> I can easily adjust the temp setting R to raise the xtal temp. But that
>>> seems like a jerry rig.
>>> Could a xtal of this quality simply go bad over time?
>>> Somewhat at a loss here.
>>> I have a spare 10544 (Would not use the z3801 outer oven)and wonder if at
>>> least I could use that with the Z3801. Anyone know if the efc would work?
>>> Regards
>>> Paul
>>> WB8TSL
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On Thu, Jul 25, 2013 at 10:28 AM, Stefan Heinzmann
>>> <stefan_heinzmann at gmx.de>wrote:
>>> 
>>>> paul swed wrote:
>>>> 
>>>>> I can't believe you found the transistor. When I pulled it out last
>> night,
>>>>> its actually a MPSA18!!! I had not had time to look it up but figured
>> it
>>>>> was a ebay leftover hunt. :-)
>>>>> At that price I may order 20 of them. Like the gain.
>>>>> 
>>>>> Toshiba used to make a transistor with even higher gain, the
>>>> 2SC3112/2SC3113/2SC3295/**2SC4666 (same chip, different package). They
>>>> discontinued it recently, however.
>>>> 
>>>> Cheers
>>>> Stefan
>>>> 
>>>> 
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