a real challange?

[Kevin Kuehn]

I'd leave that resistor as original(unconnected) for the time being, at least until you have the set operational. The 680k resistor's loose end is shown being tied to the 275v B+ in the Riders schematic, but that line is also being fed a bias voltage from the picture(contrast control) circuit. One has to assume it originally worked "as is". At some later point you can always try connecting it to B+, just to see how it affects the picture and sound.