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

[Jim Muehlberg]

Paul,

My understanding is that the 3500 V is on as soon as power is applied.  
Disconnected, I get 750V at the HV lead.  I first connected a 1M Ohm 
resistor divider because I don't really have HV measuring stuff (10K to 
1) and it read 350 V.  Indeed the meter is pegged, but I suspect that is 
due to some internal fault in the A18 as well.  So unless there is some 
turn on signal to the 3500 V supply, I suspect it is bad.  This whole 
thing may be a basket case.  No one knows the history.

I'm also missing the divider assembly, so that may put the brakes on the 
whole project, but I'll worry about that once I have attempted to pump down.

Thanks for the advice!

Jim

On 11/14/2022 3:25 PM, paul swed via time-nuts wrote:
> 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
>> F 434.296.0324
>> www.cv.nrao.edu/~jmuehlbe
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-- 

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
F 434.296.0324
www.cv.nrao.edu/~jmuehlbe