DuMont RA-105 picture distortion

[martyfreeman]

First post so be gentle. I just brought this beast back to life. Replaced all electrolytic and paper caps, DeOxIt on controls, replaced rotted zip-cord blew a ton of dust out of it.

I'm getting a good clear picture but the top inch or so has a horizontal bend to it. I've been through the typical setup (avoided touching the IF strip) to no avail. It doesn't seem to be affected by the brightness or contrast controls so I don't think the power supply is at fault.

Any ideas? Sync separator maybe?

Also, this set has a monster chassis with separate HV box. Really tough to operate out of the cabinet. I have the Photofact which cautions about pulling the horizontal oscillator to kill the HV. It suggests taping off the HV lead to avoid contact.

This suggests that the chassis can be operated disconnected from the picture tube for servicing and alignment. Is it safe to operate with the yoke unplugged? I really don't want to damage anything but pulling the chassis for every minor tweak is a real ordeal.