Tek 465 X-Y question

[Audio]

My Tek 465 will not display an x-y trace. It will display the trace when the beam finder is depressed and the
compressed trace appears to look right given the two input signals. However, I am unable to position the compressed trace to the center of the screen. The vertical position control works fine but horizontal position control will move the trace one division left or right. When I release the beam finder the traces vanishes.

Any suggestions would be appreciated.

John