Last Xmas, at my mom's house, this RCA B&W TV set with the weak CRT I used a Beltron on to make it strong.
http://www.wa2ise.com/radios/rca21t8395.jpg
Someone on this forum mentioned that CRTs with this done sometimes give out in a few weeks. The last couple of months the TV sat unpowered, and I paid Mom a visit just this weekend. So I turned the set on while I'm there. The CRT is still good. But I haven't put a week or two on it powered. It will be a while before I get that much time on it...

It's good to visit your mom...

It's good to visit your mom...

Does she still have her cats? :thmbsp:

I had a nearly dead 21amp4a that I gave a cleaning to with a cheapo Sencore tester. I ran the set nearly every day for about a year until I turned it on one day to find a weak negative image. I'd say that is a pretty typical experience for a rejuvinated tube.

I Beltroned a 21fbp22 in one of my Zenith's a while back (around 2 years). I will admit it took some serious "massaging" but it is still bright from turn on and tracking is still great.
I have wacked a few of the Sony "flashers" and most are still going. The ones that don't go a long time are some of the Samsung CRT's.

How long it will last depends on the amount of gunk that was on the cathode and what caused it to begin with. If the tube was sitting for decades not used, chances are good that you'll be able to whack it back to life and it will stay that way. Most times elevated filament voltage alone will boil off any deposits, and it will give good readings. If on the other hand the cathodes are just plain wore out from use, you might only get a temporary bump in emission before it goes back into the red. Only thing that will fix it at that point is a brightener (maybe) or a new gun.