Ok. Let’s try this again…RCA 9TC240 Alignment

[Penthode]

Originally Posted by Yamamaya42

I'm getting confused just trying to follow all this.
As Penthode said, the -4.5 is set and forget, set at the start, and don't touch, or it will throw all things off, it's meant to suppress some circuits while you do the alignment, you do not need to monitor it.

Setting it to -4.5v is simply fixing the AGC to a voltage close to normal operating voltage. The reason is that the IF response changes very slightly as you change the bias. Consider that the IF strip comprise of staggered stages employing the same vacuum tubes which have slightly different characteristics in the course of manufacture. In this world, nothing is perfect and engineering is always a practical compromise.

So the -4.5v is not an absolute. Is is a rough approximation of where it normally would be under average reception conditions.

(My philosophy: I often muse that in our digital world today, the display layer is what most now look at which is defined by a series of precise digital words which if is not corrupted in reception provides a closer to perfect ideal. Not so in the world of analog systems and television where the display layer doubles as the transport layer and is subject to vagaries like this.)