[time-nuts] HP5065a cfield issue

[Bob kb8tq]

Hi

To make any sense at all out of the synthesizer settings, you need the magic table in
the manual. They are very random and not all settings actually work ( = produce a 
stable output). 

Bob

> On Dec 1, 2020, at 3:20 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> A quick update. Several people have made very good comments. Some online
> and offline.
> Bob mentioned flipping the synthesizer switch. Heck they have been sitting
> at 8714 (Also on the tube label) for 30 years. I did  and it did not fix
> the problem. But I went through the switch seeing how each section behaved.
> By dropping to 8614 the cfield pot lines up at about 3.3 and the drift is
> semi random and small about 13 seconds for 500 ps. In this range the test
> setup is a question. The reference a TBolt to a Tek 2465b scope chnl1 and
> trigger. 5065 to chnl 2. 5ns sweep and X10 magnifier. All sorts of things
> can drift with this setup.
> Will use a 5371b counter later tonight and get serious.
> But that said have I actually lost a bit in the synthesizer. In the
> diagrams, looks like diodes and other ancient devices to consider.
> Regards
> Paul
> 
> On Tue, Dec 1, 2020 at 12:24 PM Bob kb8tq <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> Well that puts it at 5/3 = 1.3 ppb low. The C field *should*adjust over a
>> 2 ppb-ish range. Assuming you were near center, that puts the shift in the
>> “couple of ppb” range. Very much the sort of thing the synth could do.
>> 
>> Bob
>> 
>>> On Dec 1, 2020, at 9:44 AM, paul swed <paulswedb at gmail.com> wrote:
>>> 
>>> Bob
>>> I did not see your response before responding to Poul.
>>> This morning I did flip those switches and agree that I may have
>> something
>>> going on in the synthesizer. The offset that showed up is a drift of 5ns
>> in
>>> 3 seconds and its running slow.
>>> I do have the offsets from past measurements. Will have to look them up.
>>> Regards
>>> Paul.
>>> 
>>> On Tue, Dec 1, 2020 at 8:51 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>>> 
>>>> Hi
>>>> 
>>>> The C field coil resistance is low enough that you have something in the
>>>> vicinity
>>>> of 10mv across it. If you want to check the C field regulator, I’d just
>>>> pop a wire and
>>>> put a meter in series with the coil.
>>>> 
>>>> My bet: your synthesizer has slipped a bit somewhere. I’d check it’s
>> output
>>>> against the table in the manual to make sure it’s still on frequency
>>>> before I dove
>>>> into the C field. If it’s off, the switches would be my first target.
>>>> Rotate them a bit
>>>> to wipe off the contacts and see if the frequency is correct when you
>>>> reset them
>>>> to the original position.
>>>> 
>>>> If none of that works, I’d be happy to give your 5065 a new home :)
>>>> 
>>>> Bob
>>>> 
>>>>> On Nov 30, 2020, at 6:57 PM, paul swed <paulswedb at gmail.com> wrote:
>>>>> 
>>>>> Hello to the group.
>>>>> Was time for the quarterly Cesium and RB checks in an effort to support
>>>> our
>>>>> local power company.
>>>>> I discovered that there is an issue with the HP5065a Rubidium
>> reference.
>>>>> 
>>>>> The frequency has slowed and the cfield pot can not make up for the
>> jump.
>>>>> Normally a few small tick marks are ever needed. I used 3 large marks
>> and
>>>>> ran out of pot. Its at 9.9. Was at 6.14. The frequency does increate
>> with
>>>>> the cfield adjustment. I am assuming perhaps something has happened in
>>>> the
>>>>> cfield regulator.
>>>>> At least the front panel meter is indicating the +20V supply is normal.
>>>>> But my question is this. The schematic indicate very little current
>>>> travels
>>>>> through the cfield coil. Guessing far less than 3 ma. by adding up
>>>>> resistors. What I do not know yet is what is the resistance of the
>> cfield
>>>>> coil? I may find that I simply have dirty contacts on the A15 regulator
>>>>> card.
>>>>> Its possible there are other things wrong but all front panel meter
>>>>> readings look the same as they have been for years.
>>>>> 
>>>>> Thoughts?
>>>>> Thank you in advance.
>>>>> Paul
>>>>> WB8TSL
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>>> To unsubscribe, go to
>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>>> and follow the instructions there.
>>>> 
>>>> 
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>>> To unsubscribe, go to
>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>>> and follow the instructions there.
>>>> 
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts at lists.febo.com
>>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>>> and follow the instructions there.
>> 
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe, go to
>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.