[time-nuts] Fwd: Fwd: HP5061B Ion Current

[Donald E. Pauly]

https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

The -2500 supply is nearly identical to the +3500 supply.  We will
post some photos on the disassembly process.  We also had to
disassemble the +3,500 supply because the 200 Meg resistor had gone up
in value.   It showed only 1,900 V with no load when it should have
shown 3,200 V.  We replaced the 47 uFd electrolytic with a tantalum as
a preventive measure.

After we repaired the -2,500 supply we measured the output voltage
versus beam current as set by front panel adjustment. Note that about
a 10% increase in electron multiplier voltage will double beam
current.

beam current  High Voltage
30 -1,755
20 -1,658
10 -1,507

On our freshly repaired HP5061B, we ran it four hours with no voltage
on the ion pump.  It maintained lock when voltage was reapplied.  Ion
current and voltage were unchanged at 76 uA and 2500 V.  You
apparently can operate for some time with no ion pump.

Really good pix on the inside of the 3500V module. So the opening of the
can is the typical lots of heat and pry it open approach right?
How about a good pix of the 2500 Volt module?
Thanks
Paul
WB8TSL
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Re: [time-nuts] Fwd: Fwd: HP5061B Ion Current

[John Miles]

Yeah, I wouldn't worry about the oven, but the ionizer filament is a different 
story.  Those can definitely open up.

-- john,  KE5FX
Miles Design LLC


> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> Donald E. Pauly
> Sent: Wednesday, March 22, 2017 11:32 AM
> To: time-nuts; rwa...@aol.com; Donald E. Pauly
> Subject: [time-nuts] Fwd: Fwd: HP5061B Ion Current
> 
> https://www.febo.com/pipermail/time-nuts/2017-March/104374.html
> 
> I have posted two HP patents on the cesium beam tube at
> http://gonascent.com/papers/hp/US3323008.pdf and
> http://gonascent.com/papers/hp/US3397310.pdf . Both are of academic
> interest. The first claims that the cesium oven operates at 60°-70° C.
> This is a tiny heating compared to a 1,000° filament on a power
> transmitting tube.  I say that it can be cycled a million times with
> no problem of thermal cracking.
> 
> πθ°μΩω±√·Γλ
> WB0KVV
> 

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[time-nuts] Fwd: Fwd: HP5061B Ion Current

[Donald E. Pauly]

https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

I have posted two HP patents on the cesium beam tube at
http://gonascent.com/papers/hp/US3323008.pdf and
http://gonascent.com/papers/hp/US3397310.pdf . Both are of academic
interest. The first claims that the cesium oven operates at 60°-70° C.
This is a tiny heating compared to a 1,000° filament on a power
transmitting tube.  I say that it can be cycled a million times with
no problem of thermal cracking.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: John Miles 
Date: Tue, Mar 21, 2017 at 5:41 PM
Subject: Re: [time-nuts] Fwd:  HP5061B Ion Current
To: Discussion of precise time and frequency measurement
, rwa...@aol.com

That's some very nice work, Donald.  Looking back, I have junked one
or two Cs tubes that might have been usable if I'd thought through the
problem of high ion pump current as you and KB7APQ seem to have done.

Another good reason to raise the lockout threshold would be to cut
down on the repetitive ionizer filament cycling that the tube will
otherwise undergo when you first fire up the oven.  That phenomenon
always makes me rally nervous.

-- john, KE5FX
Miles Design LLC

> -snip-
> When we overrode the cesium lockout at 29 μA or so of ion current, we
> needed only minor front panel adjustments for beam current of 20 μA.
> (We shorted across A15 R-4.) Our last ion current before power supply
> modifications at risen to 39 uA.  Beam current has been stable.
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