[time-nuts] Fwd: HP5061B High Ion Current/Tubes Out of Cesium

[Donald E. Pauly]

https://www.febo.com/pipermail/time-nuts/2017-April/thread.html

We did not attempt to achieve lock because we saw absolutely no beam
current with the beam adjust all the way up.  We were running the oven
above 150° C which is more than 65° above normal oven temperatures.
Cesium pressure should have been about 30 times normal.

A photo of the A11 Cesium controller board is posted at
http://gonascent.com/papers/hp/hp5061/photos/cesiheat.jpg taken by
KB7APQ.  Note that there are no electrolytics but tantulums installed
instead.  They must have been very costly 30 years ago.  This also
prevents hard to find problems with high ESR electrolytics with age.
We have found open 47 μFd electrolytics inside two of our four HV
power supplies.  That is a place for tantalums if there ever was one.

We are working on our HP5061B's from 500 miles apart so photographs of
boards and waveforms help greatly.  The cesium oven servo is
underdamped.  It overshoots and rings down at a 10 second time
interval during temperature steps.  You can see the R12 that we
shorted out to get 150° oven temperatures for troubleshooting our
suspected bad tube.

I think that a website should be started with the collected wisdom of
this list.  I will host it if someone will maintain it. Corby's photo
graphs of dismantled beam tube parts should be on a nice web page.
If anyone has a high ion current 05061-6077 beam tube that they can
part with please contact me.  One of our beam tubes is completely out
of cesium.

πθ°μΩω±√·Γλ
WB0KVV

---------- Forwarded message ----------
From: paul swed <paulswedb @ gmail.com>
Date: Thu, Apr 6, 2017 at 5:09 PM
Subject: Re: [time-nuts] HP5061B High Ion Current/Tubes Out of Cesium
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>

Donald running higher temperatures on a a normal tube may indeed give you a
bit more life. Thats exactly how Frankenstein works. Its a hand me down
tube that normally showed as dead. Believe me it doesn't even move the
current meter and its working. My firm belief is that option 004 tubes do
not have anything left to give.

But yet with the higher temp (10-15 higher as I recall) it locks all on its
own after a good warmup period. Serious fumes.
Its been operating this way for some 4 years now. I don't run it all of the
time and I actually recently found what was wrong that always gave it a
slight offset.

So a very good conversation running here with everyone sharing really good
insights and pictures of detail I had only read about and generally without
any pictures. The entire thread should be gathered up, cleaned up, and
presented as the dummys guide to the care and feeding of old 5061s.

Regards
Paul.