Any use for 21FBP22 with poor emission?

[jhiesey]

When I got my CTC-10 set from Maguns at Stellar Electronics, he told me that the CRT (a 21FBP22) was in ok but not great shape, so he sold me an extra 21FBP22 as a spare.

I finally got around to testing the emission on both CRTs, and found the one that came in the set was pretty poor, while the spare was much better.

Just for the heck of it I bought a brightener for $10 and tested it out with the old CRT, and it did help quite a bit. But I did decide to put in the fresher tube anyway, especially since I wanted to install the safety glass that was missing when I got the set. The picture looks much better!

At 6.3V on the filament, using -50V on G1 and 50 microamps at cutoff and 0V on G1 for emission, I got the following test results on the old tube:

Red: cutoff -285V, emission 575 microamps
Green: cutoff -382V, emission 382 microamps
Blue: cutoff -315V, emission 460 microamps

Especially the green gun looks very weak (the spare tube measures almost three times better emission on all three guns, and consistent cutoff voltage on all guns of around -275V). Boosting the filament voltage up to 9V does improve the emission on the old tube significantly.

Is the old CRT a candidate for rejuvenation? Would anyone want a tube like this?

Or should I just recycle it?