[time-nuts] HP CBT Cutaway?

Robert Lutwak Lutwak at Alum.mit.edu
Sat Aug 20 11:31:35 EDT 2005

The tube is assembled and allgined on a steel rail which is subsequently 
inserted into the vacuum jacket and welded into place.  Like Rick says, if 
you need to repair the tube, you can cut off the vacuum jacket at the seams 
on a lathe and slide the whole assembly out.  This isn't the best choice for 
display, though, because you've still got two layers of magnetic shielding 
between you and the microwave cavity.

If you have access to a nice large diameter diamond saw, just cut it right 
up the middle.  This will give you a nice view of everything relevant in 
cross section.  It'll take a good saw, though, because you'll most likely be 
cutting through the AlNiCo A and B magnets along the way.  I wouldn't worry 
about filling it with anything first.  If you have a nice sharp blade, it 
won't distort anything.  Before you start, let the vacuum out by drilling a 
hole somewhere (the pinch-off is probably the easiest place since it's 
copper).  Once the air gets in, all of the cesium will turn to oxide, which 
is messy, but not particularly toxic.  In a "depleted" tube, the cesium is 
mostly adsorbed into the graphite getters, though you may end up with some 
gooey blue cesium-oxide around the oven nozzle.  Just clean it off with 
Q-tips and rubbing alcohol.

And yes, please send us some pictures when you're through.


Robert Lutwak, Senior Scientist
Symmetricom - Technology Realization Center
34 Tozer Rd.
Beverly, MA 01915
(978) 232-1461   Voice           RLutwak at Symmetricom.com   (Business)
(978) 927-4099   FAX             Lutwak at Alum.MIT.edu  (Personal)
(339) 927-7896   Mobile
----- Original Message ----- 
From: "Jim Miller" <timenuts at jcmco.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Friday, August 19, 2005 4:12 PM
Subject: [time-nuts] HP CBT Cutaway?

> Hi,
> Has anyone ever seen a cutaway of an HP 5061 CBT? I recently bought a 
> "Serviceable" 5061A from Gov. Liquidation that turned out to be  nothing 
> but an empty, gutted carcass containing only the CBT and the  time of day 
> clock option.  To add insult to injury, the CBT's leads  had been 
> close-clipped 1/2" away from the tube body.
> In order to make some lemonade from a lemon, I'd like to cut open the  CBT 
> outer case to expose the innards as a show-and-tell piece for 
> time-and-freq presentations at the local ham club and high school 
> electronics demonstrations.  Any suggestions on where to make the 
> incisions in the case? Is it worth the trouble? I have a machine shop 
> that can do the cutting.
> Thanks,
> Jim
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