1/8th of screen Missing on one game

[Netropolis]

I have a game - Memtron's Solar Warrior - a right scrolling shooter

I ACTUALLY have 2 PCB's - one just displays garbage - before I discovered John's Arcade I simply found a second PCB and bought it.
it was actually pretty reasonably priced.

This one works but 1/8 of  the right side is cut off.  it is Playable and I initially thought it was a crappy monitor, but I have since moved the PCB to a new-to-me Dynamo Cabinet with a freshly capped Monitor and the problem persists there too. 
I have 2 games in this cabinet and the other (Tetris) works just fine.  So it has to be the PCB.

My question is... Is this ONE chip? that would cause this?  I mentioned I have a second board that I COULD swap some chips out with.
The game is JAMMA and has 2 boards connected with a pair of ribbon cables (I assume one is all video).

I know it is a rare obscure game - and I am not expecting a definitive answer, but a pointer or a starting point would be fantastic.

[iankellogg]

I don't quite understand whats going on but if I had to guess i would say the addressing to the vram is messedup between the processor and vram. I'm guessing there is some kind of vram addressor that is pushing the vram out to video.
I can't find any schematics for the game so I can't answer that question online. 

[Netropolis]

Yes the PCB schematics are nowhere to be found.
but thank you - that is a good starting point.
I will swap some vram chips and see if perhaps one of the good ones on my other board fixes the issue.
Fingers crossed!  - I will report back if/when I get a full screen of Solar Warrior Goodness!

[iankellogg]

the thought has occured to me that if vram was not being written to then you would see garbage and not black. Possibly are all the chips getting power?