[time-nuts] Re: Attempting to start HP5061A {External}

[Matt Krick]

I am pleased to report that the unit is Alive and Ticking!

After 30 minutes of the cycling my unit stabilized. I have it another 2
hours of CS OFF mode and then started it again this time stable with no
cycling.

With Loop Open the Beam meter started at 2 and slowly climbed to about 15
after about 20 minutes where I did a rough tune.

After another 20 minutes I went with Oper mode and centered the coarse
tuning getting a peak meter reading of 34. Pegging control to -50

I then centered the control reading by again tuning coarse and hit the
reset button and got the continuous operation to light.

I set the clock to my watch and will compare tomorrow

On Wed, Feb 8, 2023, 15:22 Aiden Gibson via time-nuts <
time-nuts at lists.febo.com> wrote:

> Hi Matt,
>
> Just to add another 2c to this thread, I went through roughly the same
> process Jim describes with my 5061A.
>
> I also kept the hot wire ionizer powered on in order to catch any neutral
> particles which may have been affecting the vacuum.
>
> I took some measurements of the process to get a rough "pump curve" which
> can be seen here:
>
>
> https://docs.google.com/spreadsheets/d/1zsTUAiDZ92Eb-2lID9Hkoe7ByOylcx_LJ3ktGqG_uac/edit?usp=drivesdk
>
> Best of luck!
> -Aiden
>
> Sent from my Verizon, Samsung Galaxy smartphone
>
>
>
> -------- Original message --------
> From: Jim Muehlberg via time-nuts <time-nuts at lists.febo.com>
> Date: 2/8/23 17:34 (GMT-05:00)
> To: Matt Krick via time-nuts <time-nuts at lists.febo.com>
> Cc: Jim Muehlberg <jmuehlbe at nrao.edu>
> Subject: [time-nuts] Re: Attempting to start HP5061A {External}
>
> Hi Matt,
>
> I just went through this when resurrecting a 5061A option 4 that was
> about to be scrapped (Horrors!).  My ion pump power supply was flakey,
> but after I fiddled with it, I got it to work.  I then saw the same
> behaviour.  Ultimately, I connected an external supply to the ion pump
> and left it powered for a few days.  This cleaned (or whatever happens)
> the tube and I was able to lock it.  FWIW, the supply I connected was
> about 7 kV.  The label said 3KV, but apparently that was under the rated
> load.  In any event, I thought I wrecked the whole thing.  I was assured
> by some time nuts that it was OK, and it was.  It's been running
> continuously now for about 2 months.  Here's an ADEV plot for fun...
>
>    Measured against another opt 4.  Both units have an unknown history,
> and they are 40 year old tubes, so I consider this a success!  Good
> enough anyway.
>
> Good luck, and keep one hand in your pocket.
>
> Jim
>
> On 2023-02-08 12:39 AM, Matt Krick via time-nuts wrote:
> > Hello,
> >
> > I recently acquired a HP5061A and I am attempting to start it but there
> are
> > some things that are puzzling me.
> >
> > Per the manual I have left the unit plugged in for 24 hours with mode set
> > to CS OFF set to and I have observed the Ion Pump readings go to 0 after
> > about 3 or 4 minutes of first plugging it in.
> >
> > So now I am attempting to power up the tube by switching to Loop open
> and I
> > can hear another power supply engage. My Ion Pump reading climbs to about
> > 30 after about 10 seconds and then the power supply shuts off. Then I get
> > into a cycle of about 2 seconds on for 10 seconds off with the Ion Pump
> > going between 20-30 or thereabouts.
> >
> > I'm not sure if this is normal and part of the pumping down process.
> > Should I leave it on or keep trying to run it on CS OFF?
> >
> > Am I correct in assuming that with CS OFF the +3500V supply is running
> and
> > that is what is acting as the Ion Pump to evacuate the tube, and then
> when
> > I switch to Loop open that also powers  up the Cesium Heater and the
> -2500V
> > supply?
> >
> > I have experience with high power Triodes and Tetrodes where you run the
> > filaments without high voltage to help evacuate the tube so I'm unsure
> how
> > a tube like this operates.
> >
> > Thank you!
> > _______________________________________________
> > time-nuts mailing list --time-nuts at lists.febo.com
> > To unsubscribe send an email totime-nuts-leave at lists.febo.com
> --
>
> Jim Muehlberg
> Senior Engineer
>
> National Radio Astronomy Observatory
> ngVLA Local Oscillator Lead
>
> 1180 Boxwood Estates Rd B-111
> Charlottesville, VA 22903-4602
> P 434.296.0270
> C 434.422.2017
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