Not even in the same universe...

anyone know the number though ?

Something like 10 to the -6 to 10 to the -7 mm of mercury would be a decent seal-off pressure for a CRT.
jr

thats what im looking for, thanks jr tech

Looks like there's been some recent rumblings in the UK on this subject as well. Seems the gears are turning in quite a few brain pans around the world...

http://www.forum.radios-tv.co.uk/vie...hp?f=15&t=7203

Steve, I have (somewhere) internet pictures of new production 12AP4-like tubes from a decade ago, made by Thomson before they ditched RCA operations. Any idea who they were for? I believe the photos were taken in a restorer's home.

[QUOTE=Steve McVoy;3095978] Most tubes can be rebuilt successfully without re-phosphoring. Hawkeye produced high quality rebuilds while they were in business.

In some cases re-phosphoring is required. For instance, here we had some radar tubes (with P7 phosphors) rebuilt for TV use:

Ideally you want 1.e-6 (one millionth) torr.
A torr is 1/760 atmosphere. For ordinary tubes
1.e-4 torr is not "gassy" but a CRT would not like that.
1.e-2 torr of air will give a nice purple glow,
not bright but there.

The pumps used in processing will easily do 1.e-6 torr
at their inlets ... but its not easy to get that through the glass stem.

I think the glass and vacuum part would be easy compared to getting new guns. Does a source still exist? Probably in China if it does....

I have a strong interest in learning the rebuilding trade... if I could find the equipment would have no problem setting it up to to learn how to do it. I find it extremely fascinating!

Justin, keep your eyes on eBay. Rebuliding equipment comes up from time to time. I've also thought about trying to resurrect a rebuilding system some day, but turned down an opportunity to buy some equipment locally 5 or 10 years ago. I have some knowledge and experience with high vacuum and ultrahigh vacuum systems, and would happy to help with advice,troubleshooting, etc., if you find some equipment and decide to set it up at your place.

I have no idea how hard it is to find replacement guns, however.

im with you Steller, if back in the day the larger tv repair shop's had there own equitment for doing this, even if its just for black & white tubes maybe its still out there and manuals for it. and getting the equitment to vacuum it down is easy to come by ,any automotive a/c vacuum pump will 29.92'' hg or even a used refrigerator compressor will vac down to 29.92"hg =760 torr at 0 sea level .witch is more than enough .

Einar72, we had those tubes made for collectors:

http://www.earlytelevision.org/12ap4_substitute.html

As for the availability of guns, ones for the old tubes are no longer being made. There are an unknown quantity out there - from shut down rebuilding facilities. We have been able to purchase some of them.

The other approach is to use the old gun and replace the cathode and heater, both of which are still being made, but for how long no one knows. We are attempting to buy a stock of these.

Not even close... read my post above, it is difficult to express exponentials on this site. When I wrote 10 to the -6 mm of Hg, this. means 1 millionth of of a torr:

"One millionth is equal to 0.000 001, or 1 x 10−6 in scientific notation. It is the
reciprocal of a million, can be also written as 1/1 000 000. Units using this fraction"

jr

heres i hope a chart i found, when i was in G.M. or oldsmobile a/c training yrs back to remove all moister from desacent we had to boil cold water at-30inch or 29.92 of vacuum thats alot more than it sounds the chart i found puts 760 torr on the same scale as 29.92 if its not what in inch are crt vacuum down too . there's some interesting video's on youtube of rail cars emploding with low vacuum, type in [ rails cars emploding ]

Nice chart, Again 10 to the -6 is about what is needed to process a CRT, and simply put you can't get there with a simple mechanical pump such as those used to pump refrigeration systems. Most CRT processing stations use a diffusion pump, sometimes with a Ln2 cold trap.
Now the mechanical gauge on such a system *may indicate* a "perfect vacuum", but really it is not capable of making a precise measurement. It would sort of like trying to measure the speed of light with a stopwatch! A decent ion gauge is needed to measure high vacuum, *not* a barometer type mechanical gauge.
jr

Ion Gauge : http://en.wikipedia.org/wiki/Hot-fil...nization_gauge
Diffusion pump: http://en.wikipedia.org/wiki/Diffusion_pump