pin 9 on U8 is for the "dot" on display 2.

Connector J3 is split into 2 halves, pin 1 is ground, pin 2 is 5V logic, then pins 3 - 10 are all for display 2 - the rest 11 - 26 are for display 1.

The buffer chips have all been replaced, but, you say you put 4049 in there??

Schematic has them listed as 4050 which is non inverting - the 4049 is an inverter,
schematics clearly show these as definately non inverting, both listed and on diagram.

...I printed off the diagram for your machine as this part differs to my space station

Also do you have signal going into J3? - follow it back through connections. You have lost signals from somewhere either at this connector or before it. BUT, once you get the signal back, if the right chip is not on place at U8 etc, then all youll get is garbage displayed