[time-nuts] 5071A tube EEPROM and tube data

Dave Carlson dgcarlson at sbcglobal.net
Thu Sep 10 06:30:30 UTC 2009

Corby wrote: "I'm not saying other tubes dont have glass but HP tubes DO 

On what authority? That statement is categorically incorrect.

To set the record straight I worked for HP and Agilent since 1977 as a 
technician on the 5061 and later worked on the introduction of the 5071A 
with the newer small-format CBT needed for that chassis. I've had direct 
contact with the physicists, engineers, glass-blowers, and assemblers of the 
CBT and have handled the components that make up a CBT. I've given 
presentations to Agilent Sales Engineers at neophyte seminars, given 
training on the physics principles of the CBT and have learned what I know 
from the people who created the Cesium Beam Tube. I think I know what goes 
inside an HP or Agilent CBT.

The ampoules are glass. They are filled using a "cow"  that is a string of 
several ampoules  that are simply a bulge in the end of a glass tube. When 
all the ampoules are filled   with exactly the correct amount of cesium, 
they are each "calved" off the string using a glass-blowing torch. It's a 
fascinating process and would not work if the ampoules were metal.

Now I'll concede that at some time in the past HP may have switched their 
process from a metal to a glass ampoule, and you should know if you indeed 
pulled that oven from an older HP CBT. But don't say that HP doesn't used 
glass. That's absolutely wrong. They did when they were HP, and continued to 
do so when they became Agilent. I was there.

Dave Carlson

From: "Corby Dawson" <cdelect at juno.com>
To: <time-nuts at febo.com>
Sent: Wednesday, September 09, 2009 14:00
Subject: [time-nuts] 5071A tube EEPROM and tube data

"The HP tubes used a heated metal "burst" diaphragm not glass ampoules


Actually, YES.

I dug up the oven I had opened up and it is as I remembered.

The cesium ampoule is all metal and sits upside down in the center of the
"wicking" screen.

The center of the burst diaphragm is welded to a post that comes out the
top of the oven via an insulated feedthru.

When they want to free the cesium they apply a high current thru the post
and it melts a hole where the post was welded to the diaphragm.

NO glass inside the wicking or inside the ampoule.

I'm not saying other tubes dont have glass but HP tubes DO NOT.

I'll see if I can look thru my box of ovens and if I have an FTS oven
I'll cut it open and see.

Corby Dawson

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