Zenith H2447R 19" Porthole TV

[benman94]

Another thing to keep in mind: sometimes these tubes were last used 60+ years ago and have developed a very minor, and expected, case of cathode poisoning. The typical current draw of a tester is usually insufficient to bring the tube back up. Either forcing the tube to wake up via elevated heater voltage, cleaning it by pulling more current from the cathode a la the Beltron, running the tube on a working chassis with HV to clean up the cathode or some combination of the three is necessary to really get a tube working again.

My own two "dead" CRT stories: I won a 16AP4 at the ETF auction a few years ago that has been tested by some guy with a CR-7000. He wrote it off as a lost cause; it had low emissions and bad cutoff.

I won it for $5 or $10, cleaned it on the Beltron. Now it tests like a brand new tube, has excellent cutoff, and is residing in a nice little Emerson producing a flawless image.

The big Westy you just delivered for me looked poor on Beltron initially. Knowing I'd never find another 24AP4, I decided to bring the set up on a Variac. The tube is nice and bright, actually so bright it's irritating to look at.

I retested it on the Beltron after unplugging the set and going away for the weekend. This morning it read right at the top of the scale with a 30ish second life test. It just needed a good "scrubbing" of the cathode and just running the set for 4 minutes or so must have been sufficient to clear up the cathode.

Again, recap and run it. I think you likely have a good tube.