[time-nuts] HP5065a cfield issue

[paul swed]

For everyone when the cfield pot is at 0.0 its 2.5ma and at 9.9 its 6.38ma.
The jump is over 4 major divisions of the cfield pot and I still did not
match the reference..
So looking at the synth chart on page 3-9 started to see how far it had
gone.
Tube says the switch should be 8714 or -240 E-10 the switch setting that
works well is 7698 and that represents -230 E-10. Thats quite a change. But
the Cfield matches the reference at 3.5 and that takes 6 min and 53 seconds
to move 5ns. Could do better but ran out of time tonight) Its still
slightly fast. The green cont op lights and stays lit. Some of the chart
settings do not light the con op light. Will see if the unit actually stays
stable overnight or does it speed up or slow down.
If it does thats going to be tough to find.
Thanks everyone so far for your help.
Paul.

On Wed, Dec 2, 2020 at 7:51 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> Ok, if that still turns out to be correct … that’s just about 2 ppb. (
> 1.6667…).
> To do that with the C field, you would need to make a *major* change. It’s
> essentially the whole range of the pot. You already know that it’s off in
> the
> direction of needing more counts on the dial. I *think* the current is
> lowest
> at that end, but I could easily be wrong. Either you need zero current or
> 2X normal. Either way that should be easy to spot.
>
> Bob
>
>
>
> > On Dec 2, 2020, at 2:59 PM, paul swed <paulswedb at gmail.com> wrote:
> >
> > Yes absolutely it can go back and it is the same offset. I can get real
> > numbers from memory 3 seconds for 5ns drift and the units slow. Will
> > confirm and reshare.
> > Regards
> > Paul.
> >
> >
> > On Wed, Dec 2, 2020 at 2:52 PM Bob kb8tq <kb8tq at n1k.org> wrote:
> >
> >> Hi
> >>
> >> Just double checking….. Are we still after a change went past 1/3 of the
> >> pot range?
> >>
> >> Can we get the pot back to the original location and measure the
> frequency
> >> offset
> >> (even if only in a crude fashion)?
> >>
> >> Best guess is still that this should be a ppb or more of shift. If it’s
> >> down in the
> >> 4x10^-11 range then indeed, there’s something off in the C Field setup.
> >>
> >> Bob
> >>
> >>> On Dec 2, 2020, at 2:03 PM, paul swed <paulswedb at gmail.com> wrote:
> >>>
> >>> Corby will check. Though in looking at the cfield circuits it does
> appear
> >>> all to be correct. Its some other odd offset that has crept in.
> >>> Thanks
> >>>
> >>> On Wed, Dec 2, 2020 at 1:56 PM <cdelect at juno.com> wrote:
> >>>
> >>>> Paul,
> >>>>
> >>>> One other thing to check.
> >>>>
> >>>> Put a DC coupled scope on the C-field pot wiper and rotate the pot
> back
> >>>> and forth.
> >>>>
> >>>> Make sure there are no jumps or noise.
> >>>>
> >>>> Sometimes the pot gets noisy in a section.
> >>>>
> >>>> Rotating it back and forth across the bad sections will usually clean
> it
> >>>> up.
> >>>>
> >>>> Cheers,
> >>>>
> >>>> Corby
> >>>>
> >>>>
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