Well, after spending half a day changing neckboards, zener diodes, reflowing suspcious solder joints.... I've finally got some progress.
Here's what I did initially.
1. Initially did a continuity test from the Jamma edge (Pin 12 on Solder side) to the Chassis connector. Got beep = Jamma wiring is good!
2. I reflowed some suspicious soldering points on the replacement neckboard and was able to get Blue which is a start....
3. I then decided to change the neckboard of the original which came with the blast and after 30 seconds after switching on, the picture turned off and smoke started to emit from the back. Shocked, I immediately turned the power off, but regrettably couldn't see the exact location of where the smoke came from. I figured I should turn the power off first to avoid any irreversible damage to the tube.
4. Since I believe the original chassis and tube were killed due to the chassis being faulty, I was going to assume the worst and that my replacement tube was also cracked like the original. I switched back to the replacement neckboard and thank god, the tube is still alive!
I played around with the RGB settings and the flyback screen controller and ended up with this result:
I noticed that the Blue bar is now bleeding to the right side of the screen and the text is doing the same too. Running the game shows it looks much better than before with just the yellow tint, but yeah, will need to wait till next weekend to work on this again.
But yeah......PROGRESS!