[time-nuts] HP5065a cfield issue

[paul swed]

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
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