The older F40T12DX failed last week in the lag side. Monday I noted that the "newer" CXL lamp had started to make tear shape spots on the each side of the bulb, and I was getting some purple flashes. I started the lamp a few times and it seemed fine. I was off yesterday and didn't check when I came by. Today it's DEAD and very black on the dead cathode end. Usually an EOL will break the cathode on the lead side, which it was in.  I guess I have to find something else to go in that side now.  

Before that there was only brown smudges on the ends. I guess somewhere in 24/7 service maybe 5000 hours. A year is 8760. Not good.  Some of the ACE GEs are doing 3 to 5 years in 18 hour daily service.   

This is common, that before the lamp reaches EOL, there are little blackening and when reaching EOL, suddenly there are much blackening on the deplated emitter electrode. This was also happened on the US Philips F40T12/D on the fixture with the Shaingout Electronic-Start preheat ballast with an electronic starter, in the storage of Carmel hospital.
The huge blackening when the lamp is dead, caused by the sputtering of the electrode itself, and not from the emitter. The sputtering of the electrode itself is much faster than that of the emitter.

They must have forgotten to put enough  material on the cathode on this one.  These are small double coiled cathodes. I was hoping for some end banding.  One of the previous lamps I removed for fear of EOL had tear drop spots ( large ones eventually) that eventually burned the phosphors.

Thes are $1.76 each so I got 2 and dated them with a Sharpie.  Now I can tell what the real life will be.

The first one wanted to rectify and super swirl and went out multiple tims . The starter tried a few times and finally heated the cathodes enough to work. The other one was OK.

Life?  Where is my stopwatch !

Powell