[charokeeroad]

I may be able to help. I've tested several 21" Predicta tubes in the last few weeks with a B&K 465. It will take me an hour or so to put all the pieces together but I think it will give you the info your looking for. I'll post pieces at a time so here goes. First, two pictures of the adapter. The heater pins on the adapter are marked on the adapter as 1 and 2 but I think it's better described as the sockets on each side of the key. These pins are the same for the 2.3V CRT and the 6V CRT. My set up data doesn't call out any differences in the wiring between the 6V and the 2.3volt.

On my adapter you can see that I cut into the black lead which is one of the heater leads and added some wire and some clips. I use these clips to do a current measurement as I'm testing the CRT.