12UP4 condition

[EdKozk2]

I finished recapping a Zenith 23G24 chassis this week. I used a 5AXP4 test crt to check everything out. Brightness, contrast,and volume controls all work correctly. The set came with a 12UP4A metal cone crt, Rauland. The 12UP4 tested zero for emissions, but the filament works fine. I decided to give the 12UP4 a try in the Zenith chassis. After adjusting the ion trap I was able to get a very dark picture. Only viewable in a dark room. The contrast control worked fine, but the brightness had no effect on the image. I decided to try a brightener. The brightener increased the brightness level IMO 100% from what it was at. The picture is bright enough to have a small lamp lit in the room. Even with the brightener I still have the issue with the brightness control.It has no effect,it is static. This chassis has the brightness control connected to the cathode, pin 11. The set has 9KV on the anode. Has anyone else ever had total loss of brightness control from an extremely weak crt? I was going to use the old 12UP4 with a brightener till it dies. The first picture is with a brightener being used. The second with the camera set for increased exposure duration. The actual image brightness is between the first and second photo.
Ed