OK, now I'm curious.
using the CTC-16-XL schematic as reference.
https://i.imgur.com/VgMbCbL.jpg
the HV Rect circuit is the same as the CTC-15/GE except for one thing,
the red X es are the resistors i intend to replace to try to get HV regulation stable.
the circles are the difference in the 15- > 16
in the 16, the 1 k ohm resistor off the shunt cathode goes directly to the bias point (390v), in the 15, its tied to the same source as the damper, which goes up to the green wire in the vert output transformer, which has an indirect link to the bias point via the centering pot, etc.
any clue why they changed this for the 16?