Revisiting an old topic - Adding DC Restoration to a 1950s TV

[maxhifi]

Originally Posted by Penthode

But can you say if the brightness control is near one end or the other? That is assuming before the modification the control was roughly central.

It is turned up almost all the way, but that was also the case before the modification. I think it has slightly less range on the high end now though

[Penthode]

That makes sense. The CRT is closer to cut off and the wiper is at the ground end. Placing a little plus DC bias on the CRT control grid will centralize the control. The diagram is cut off but I suspect the grid goes to ground through a resistor with a coupling capacitor from the vertical output transformer feeding it?

Placing a single additional high value resistor between the +250v rail and the CRT control grid will form a resistive divider which should apply a positive bias of roughly +20 volts on the grid. This will bring the brightness control closer to the center of its range.