Tektronix T922 calibration

[Zeyneb]

Dear people,

I'm having a Tektronix T922 scope and the trace rotation potentiometer was falling apart so I was able to replace that one. It's nice to solder on such an older (through hole) technology board. Actually I took the Y-axis potentiometer off, also 2K, and soldered that into the trace rotation position. For the Y-axis function I installed a new multi-turn potentiometer because these pins where 0.1" pitch in a single line.

I successfully managed to put the crt & vertical amplifier board back together. And applied mains power to the scope. Now the trace rotation can be set properly but the problem I'm facing is to understand the terminology in the service manual regarding the Y-axis alignment calibration.

Here is the link for that service manual:
www.logwell.com/tech/oscilloscopes/t921_922_sm.pdf

Now I'm on page 52 of that with the paragraph title "4. Y-Axis Alignment"

For now I just have a basic function generator set to some 5 kHz square wave. I also need to install some 50 ohm terminator resistor to do this properly.

If I turn on the Y-axis potentiometer I see a feature similar to the vertical position knob on the front panel. Is that what it is supposed to do?

From the instructions in the manual I don't understand the terms baseline and marker.

In particular the steps e and f are problematic to me:

"
e. ADJUST-Y-Axis, R474, (see Fig. 4-3) to align center marker with center vertical graticule line.
f. INTERACTION-Position display baseline to center horizontal graticule line and check that baseline aligns with horizontal graticule line. If not, re-adjust trace rotation. Then re-check Y-axis alignment.
"

I understand center vertical/horizontal graticule line. But what is "center marker" exactly?
As I do not have a time-mark generator should I set the function generator to swing to a negative voltage during the low period of the square wave or should that be 0V?

Thank you very much for your attention and time!

Best regards,
Zeyneb