Don't worry about asking questions here, we share what we know and can always learn more about the art
My main concern is damaging vintage test equipment doing these measurements because there can be several traps which we are discussing.
You can add the 2:1 divider ahead of things, but it will actually read 1/3 because the scope ends up a 1MEG load in parallel with the 1MEG lower divider resistor giving 500k.
If you try measure signal on a gain stage's plate, it will get loaded down somewhat.
I realized the 100:1 probe is actually a bad idea. AC-coupled, a scope's input cap will charge to the full DC potential regardless of the probe attenuation, if it's 1x, 10x, 100x because the cap is
ahead of the scope's 1MEG front-end resistor. This is a trap.
If you have any drama with the Leader, check it's PSU rail voltages are OK and then I go after the old Marcon caps.