Substitute 12KP4 for a 12LP4

[bandersen]

I recently picked up this 12KP4. It tests very good on my Sencore CR70 - plenty of emission and grid control. However, when I popped it into a worked set in place of it's 12LP4, I'm getting nothing

The specs look nearly identical on paper. The filament is glowing and I have ~10 KV at the anode. Maybe it's the lack of the DAG coating ? The previous owner removed it all to put the CRT on display. This set does have a doorknob cap on the HV so I figure it shouldn't make much difference.

Also, the 12KP4 takes slightly more focus current, but that shouldn't matter much - should it ?

Here are the specs: 12LP4 12KP4