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

[Penthode]

I see the x-y inputs to the scope and you have a trace. To confirm the trace sweep is from the HP8601a: the scope is in x-y mode? If you remove the cable to the Ch1 input the trace descends to a dot?

If so, the display you show looks very much like it includes a marker. What have you selected on the 8600a? The control with the button depressed, if you rotate it does the dot move?

Please confirm this before we move on.