Yes, there is a separate filament supply (Y and Z) for the damper tube and kinescope (the other tube filaments are supplied by connecting to the X supply and ground):
I think I read somewhere that a damper is given a separate filament supply to reduce the risk of heater-to-cathode shorts, when its cathode is at hundreds of volts above ground.
The schematic seems to show that C62 connects to ground in some models and to the +255vdc source in other models:
A note elsewhere says, "Dotted in parts are not used in all models. When dotted in parts are used, points marked X are broken." In other words, that leg of C62 would connect either to +255vdc or to ground, depending on model.
Referring back to the first picture, the +255vdc source is separate, not the same as the Y filament source that connects to pin 7 of the damper. So, if I follow this correctly, connecting C62 between pins 3 and 7 is not right for either model.
Here is a bigger chunk of the schematic showing other dotted-in stuff:
http://antiqueradio.org/art/temp/Majestic1600.jpg
There you see that C61 is like C62, connecting either to +255vdc or to ground, depending on model. Parts R95, R97, and C71 are also dotted. Perhaps if you check how all those components are connected in your set (and whether R97 and C71 are even present), that will give a clue how to connect C62.
Phil Nelson