Update...
Tested the board in a working Tempest, and determined the Vector Generator board contains the fault. Aux board and board connector cable are both verified good.
In the machine I tested in, my board showed horizontal collapse, as opposed to what you see in the video.
Since bringing it back home, I cleaned and reseated 5 RAMs that were socketed. Now, I have no X/Y output voltage at all (I had scrolling voltages before). Game still plays blind. I simply have no XY output anymore.
I tested a bunch of chips in the Vector Generator Address Selector, Data Shifter, and Vector Timer sections of the board using a logic comparator, which all tested good. I don't have every 74LS chip that is used on the board so I can't test all sections, but I feel like some main problem areas are eliminated.
Logic probe confirms data is flowing in the RAMs and the vector generator sections.
One strange area is the outputs of D5, D6 and E5 (Vector Generator Data shifter section) which is 3 LS194 chips that go to the Vector Generator XY output section. Data is pulsing on the inputs, but all outputs read low. I don't know if this is normal or not...but to me it seems not.
Any suggestions on what to try next, or did I miss something big here??
Vector gurus....please help!