Bad Dudes Vs. DragonNinja repair log

Some days ago I had on the bench this Bad Dudes PCB for a repair:

Board played fine but  clearly had color palette troubles which I narrowed in CPU board by swapped a good one:

Putting my fingers on board some colors were changing so I could locate the palette RAMs in three TMM2018 chips:

Probing the chips I found that pin 6 (address line A2 in common) of all of them was completely silent, this was confirmed also by my scope:

According schematics this signal should come from pin 9 of a near 74LS157 @15H :

but I couldn’t measure any continuity with my multimeter.A closer inspection revealed some corrosion on pin 6 of the TMM2018 @IC78 :

ac

I removed the chip and found that the pad was completely corroded and lost contact with its traces:

I promptly patched them and this fixed the game completely: