I have an unmarked 16" metal bell CRT with a "Z" painted on it. I'm pretty sure it's a 16GP4 just going by the dimensions.

I tested it with my Sencore CR70 and have absolutely 0 emissions. I suspect there's either an internal break in the cathode or it's completely worn out.

I then tried every trick I know of:

Touched up the base pins with a soldering iron - no effect
Pulled off the base to look for a break inside - nope
Rejuvination - no effect
Auto-restore - no effect
Even tried to reweld the cathode from every angle with no luck.

Anyone have anymore ideas ?

http://farm8.staticflickr.com/7219/7134158535_9d1394e670_z.jpg (http://www.flickr.com/photos/70039806@N00/7134158535/)

You've tried everything I would have tried. I guess you could get one of those old atomic blast rejuvenators from the '60's and try that. You certainly have nothing to lose at this point.

I had one like that too, zero emissions no matter how high the heater voltage, wouldn't rejuv, tried it in a set, nada.

I suspect these metal tubes sometimes get a microscopic amount of gas in them and it kills them dead even though they don't glow purple and the getter is OK.

Mine looked like it had been stored very poorly, rusty and dirty, I didn't expect it would work and I was right.

I reattached the base, hooked it up to an old B&K 440 and got a nice light show!
The indicator lights seem to show a heater G2 short.
http://farm8.staticflickr.com/7270/6990590950_ea37803f61_z.jpg (http://www.flickr.com/photos/70039806@N00/6990590950/)

Nice and gassy! I suspect that's also the cause of the short reading.

Yep, definitely gassy and the filament has now burned out.
So do I hang on to it on the slim chance it might be rebuilt or sell it to some local steampunk artist :scratch2:

CRT baseball anyone? :D

Yep, definitely gassy and the filament has now burned out.
So do I hang on to it on the slim chance it might be rebuilt or sell it to some local steampunk artist :scratch2:

If the thing has air in it, I wouldn't try to get it rebuilt.:nono:

If the thing has air in it, I wouldn't try to get it rebuilt.:nono:

That's a very good point. The metal glass seal is probably leaky.