[time-nuts] Re: James Miller/Brooks Shera 10 MHz GPSDO

[David G. McGaw]

Actually, a standard single-oven 10811 is quite easy to take apart and 
repair (if necessary).  It is the double-oven version that is hard to 
get into the inner oven.

The 10811A operating and service manual is here: 
https://www.keysight.com/us/en/assets/9018-02627/user-manuals/9018-02627.pdf

David N1HAC

On 9/2/22 4:45 AM, Mervyn Thomas via time-nuts wrote:
> Bob,
>
> I'm with you on that and although I have 2 10811's I would be loathe 
> to tear one apart - certainly as a last resort only and for 
> information sake rather than being able to fix it.
>
> Merv
>
> On 2/09/2022 4:55 am, Bob kb8tq via time-nuts wrote:
>> Hi
>>
>> The version you have simply has a “box” around a fairly normal
>> 10811 OCXO. Tearing it apart is possible. It isn’t a whole lot of fun
>> though.
>>
>> I still believe that the GPSDO board should put out +/- voltages
>> and not just a negative voltage. Positive tune voltages are pretty
>> common. Bipolar tune is unusual but not unheard of. Negative
>> only tune is *very* rare.  Since the board is already out in the open,
>> working on it should be easier than ripping open the OCXO.
>>
>> Bob
>>
>>> On Aug 31, 2022, at 11:21 PM, Mervyn Thomas via time-nuts 
>>> <time-nuts at lists.febo.com> wrote:
>>>
>>> Hi Bob,
>>>
>>> I need to find a schematic to download for my particular version of 
>>> the HP oscillator
>>>
>>> Merv
>>>
>>> On 31/08/2022 2:59 am, Bob kb8tq via time-nuts wrote:
>>>> Hi
>>>>
>>>> If you check the 10811 schematic, the varicap is biased at roughly 
>>>> +6.8V internally.
>>>> The other side of the diode is what the EFC is driving. This gives 
>>>> them the +/- 5V
>>>> range they specify on the 10811 data sheet.
>>>>
>>>> Bob
>>>>
>>>>> On Aug 30, 2022, at 5:39 AM, paul swed via time-nuts 
>>>>> <time-nuts at lists.febo.com> wrote:
>>>>>
>>>>> Pretty clever approach to establishing an offset. But doesn't it 
>>>>> matter how
>>>>> the vari-cap is hooked up in the oscillator circuit? If the 
>>>>> veri-cap needs
>>>>> a negative voltage to work that may indicate the cathode is at 
>>>>> ground and
>>>>> the positive voltage would forward bias the vari-cap. Just 
>>>>> thinking about
>>>>> the possible impact.
>>>>> Though the cost of experimenting is $0. No harm.
>>>>> Regards
>>>>> Paul
>>>>> WB8TSL
>>>>>
>>>>> On Tue, Aug 30, 2022 at 1:22 AM Mervyn Thomas via time-nuts <
>>>>> time-nuts at lists.febo.com> wrote:
>>>>>
>>>>>> Stephen,
>>>>>>
>>>>>> An idea I may try -thanks for your response.  The current 
>>>>>> involved in
>>>>>> the EFC line to the oscillator is extremely small-button cells would
>>>>>> last years.
>>>>>>
>>>>>> Merv
>>>>>>
>>>>>> On 29/08/2022 8:42 pm, Stephen C. Menasian via time-nuts wrote:
>>>>>>> Merv,
>>>>>>>
>>>>>>> If I understand your problem, the 10811's VCO control input 
>>>>>>> voltage has
>>>>>>> drifted above the output range of the GPSD driver board. If the VCO
>>>>>>> control terminal current is low enough, you might be able to 
>>>>>>> quickly
>>>>>> solve
>>>>>>> this problem by putting 1 or 2 Lithium Ion Coin cells in series 
>>>>>>> with the
>>>>>>> control lead. If only a few microamperes are involved, this 
>>>>>>> solutin might
>>>>>>> last several years.
>>>>>>>
>>>>>>> Stephen Menasian
>>>>>>>
>>>>>>> On Mon, 29 Aug 2022 15:56:52 +0800
>>>>>>> Mervyn Thomas via time-nuts <time-nuts at lists.febo.com> wrote:
>>>>>>>
>>>>>>>> Hi Bill,
>>>>>>>>
>>>>>>>> Unfortunately the 2 HP 10811's I have have no way to poke 
>>>>>>>> anything thru
>>>>>>>> the can to adjust a capacitor.  They are completely enclosed in an
>>>>>>>> aluminium can with 2 power leads coming out with 6 pin female
>>>>>>>> connectors on the end which go to the power board as used in 
>>>>>>>> the HP
>>>>>>>> Z3801 GPSDO and 2 thin coax cables with SMB connectors - one 
>>>>>>>> marked as
>>>>>>>> 10 MHz and the other as EFC.  I may have to replace mine with 
>>>>>>>> the model
>>>>>>>> that has the tuning capacitor.
>>>>>>>>
>>>>>>>> Thanks for your response.
>>>>>>>>
>>>>>>>> 73Â Â  Merv
>>>>>>>>
>>>>>>>> On 29/08/2022 12:45 pm, Bill Beam via time-nuts wrote:
>>>>>>>>> I also run a Brooks Shera/HP 10811. Still going after many years.
>>>>>>>>> You must live with the limited steering voltage.
>>>>>>>>> The solution is to adjust the HP 10811 tuning capacitor to get it
>>>>>>>>> back near a frequency that the EFC can handle.
>>>>>>>>> I have had to do this more than once.  Also if replacing the
>>>>>>>>> oscillator its tuning capacitor may need adjustment.
>>>>>>>>>
>>>>>>>>> On Mon, 29 Aug 2022 11:25:26 +0800, Mervyn Thomas via 
>>>>>>>>> time-nuts wrote:
>>>>>>>>>
>>>>>>>>>> Hi All,
>>>>>>>>>> I'm new to time nuts but here goes.
>>>>>>>>>> I built a GPS disciplined-Â  10MHz osc about 15 + years ago.-Â  It
>>>>>>>>>> uses an HP 10811 D/Oven Oscillator and the Brooks Shera PCB and
>>>>>>>>>> software V402N.- The physical construction article was per James
>>>>>>>>>> Miller G3RUH. This unit has worked flawlessly for all these 
>>>>>>>>>> years
>>>>>>>>>> but now is unable to hold the freq to precisely 10MHz - it is
>>>>>>>>>> constantly .29 to.60 Hz high.- The DAC output which controls 
>>>>>>>>>> the EFC
>>>>>>>>>> into the osc outputs a negative only adjustable voltage 
>>>>>>>>>> between -3v
>>>>>>>>>> down to 0V and is settable by varying a 10K potentiometer.-Â  The
>>>>>>>>>> Osc. now needs abouit +0.46V to bring it down to 10MHz but 
>>>>>>>>>> the DAC
>>>>>>>>>> does not seem able to output a positive voltage.-Â  The DAC is an
>>>>>>>>>> AD1861 (obsolete) and has a +5V applied to pin 16 and a -5V 
>>>>>>>>>> applied
>>>>>>>>>> to pins 1 and 8. My first reaction was the HP osc. had 
>>>>>>>>>> reached the
>>>>>>>>>> end of it's life but the datasheet states the EFC control 
>>>>>>>>>> voltage
>>>>>>>>>> can be between a plus 5V and a minus 5V which varies the freq 
>>>>>>>>>> by 1Hz
>>>>>>>>>> so it seems it is just over half way through it's life.
>>>>>>>>>> I feel the Brooks s/ware would have provided some method to 
>>>>>>>>>> ensure
>>>>>>>>>> the DAC output could be adjusted to swing the full full 5V or at
>>>>>>>>>> least 3V?- I have the source code but I'm no programmer so would
>>>>>>>>>> appreciate any help someone can provide please.
>>>>>>>>>> 73 de Merv-Â  VK6BMT
>>>>>>>>>> _______________________________________________
>>>>>>>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>>>>>>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>>>>>>>>> Bill Beam
>>>>>>>>> NL7F
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>>>>>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>>>>>>>> _______________________________________________
>>>>>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>>>>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>>>>>>> _______________________________________________
>>>>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>>>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>>>>>> _______________________________________________
>>>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe send an email to time-nuts-leave at lists.febo.com