Hoffman TV - Improper Picture Height

Hi all. I recently bought a vintage Hoffman television from a house sale and it works great except for improper height of picture, which my Sylvania TV Repair Booklet says could be caused by improper voltages supplied by low power supply, resistors changing their values, or bad vert osc tube. I tried adjusting vert hold and vert linearity and the picture is maxxed at about 50-per-cent of the screen height, centered in the screen.

I am wondering if anyone else has had this problem and if it might just be a bad tube or other part?

Also, I have heard of people changing all the electrolytic condensers in old equipment as one of the first things they do. Is that really necessary or could I let it go? I really don't want to be installing new stuff in this set (yes I am aware of drilling out old condenser cases and hiding new ones inside).
Thanks in advance for any help!