[time-nuts] Re: 5061A HV Supply, et al. {External}

[paul swed]

Jim
I may be missing something here. Your suggesting the 3500 V ion pump supply
is bad.
But I believe the ion pump meter is pegged from an earlier post. If true
then the 3500 V is fine. If the tubes dirty and drawing too much current
there is a lockout circuit on a15 that will not allow the CS oven and 2500
V to come up until the ion pump is below about 15-20ua on the meter. It
senses the current being drawn by the 3500 HV. Enters a15 on pin 1 and
inhibits the rest of the system.
If my thoughts are correct then you need to pump down the tube as Rodger
says with a 3500 V supply and as I suggested 300 ua is way more than
enough. There is a chance the tube may work in a relative quality sense.
That is it could lock but there are so few Cs that the output of the system
is noisy.

Regards
Paul
WB8TSL


On Mon, Nov 14, 2022 at 3:00 PM Jim Muehlberg via time-nuts <
time-nuts at lists.febo.com> wrote:

> Rodger,
>
> Thanks for the encouragement!  I'm trying not to spend too much effort
> on this - sort of a distraction from real work.  One would think that
> NRAO would have a HV power supply lying around somewhere, but astronomy
> has gone solid state now for decades!  We have a grad student trying to
> nurse along another 5061 and we'd like to have a pair. I guess I'll
> slice open the A18 module and see what makes it tick.
>
> Thanks again,
>
> Jim
>
> On 11/10/2022 9:11 AM, Rodger via time-nuts wrote:
> > Hey Jim,
> >
> > I got a 5061a a couple years ago with high ION pump current.  In my case
> the 3500 volts was there but the tube was not pumping down, even after
> being on for weeks.  I found a Terranova 741 Ion pump power supply on eBay
> for under $100.  It was listed as not working but worked AOK when I got
> it.  It's a nice supply with variable output voltage, current limiting,
> safety interlocks, etc.  I hooked it up to the tube and let it run for a
> few weeks.  Tube pumped down successfully and is working AOK now.  My guess
> is that my A18 wasn't capable of supplying the current needed to pump down
> the tube but the external power supply was.
> >
> > Note: I proceeded very carefully with the external supply, letting it
> run for days at lower voltages and gradually working up to 3500.  Also, I
> kept the current limit set as low as it would go.  Anyway, it worked for
> me.  Good luck with yours.
> >
> > Rodger
> >
> > -----Original Message-----
> > From: Jim Muehlberg via time-nuts <time-nuts at lists.febo.com>
> > Sent: Wednesday, November 9, 2022 11:07 AM
> > To: time-nuts at lists.febo.com
> > Cc: Jim Muehlberg <jmuehlbe at nrao.edu>
> > Subject: [time-nuts] 5061A HV Supply, et al.
> >
> > I've recently come into possession of a 5061A.  It is claimed that the
> tube is exhausted, but I'm unwilling to scrap it (horrors!) yet.  I'm not
> well equipped for HV measurements, but it appears the +3500 V supply is not
> working.  So, I'm hoping the tube just needs to be pumped since it hasn't
> been powered for years.  Also missing the A3 assembly, but I'll worry about
> that later...
> >
> > Anyone willing to part with their A18 or loan it to me?
> >
> > Thanks!
> >
> --
>
> 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
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> www.cv.nrao.edu/~jmuehlbe
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