At power up I was greeted by a black screen and no sound.
This board was populated by a lot of Fujitsu chips... First step was to identify and replace all the dead Fujitsu chips. After a first batch (around 20 ICs) I managed to get something on screen:
Then I had to change more bad Fujitsu chips with floating inputs, harder to diagnose.
Each time I ran the game in the hope of any improvement:
To finally obtain correct graphics:
The battle wasn't over as the game was still silent. The audio RAM @ 3F (on top board) was dead. Replacing it restored the sound.