Mr. Do's Wild Ride repair log

Received for repair an original Mr. Do's Wild Ride PCB, a game released in 1984 as the third chapter in Universal's Mr. Do! arcade series  :

Board booted up, game was playable with sound too (I hooked up an external audio amplifier since the board lacks of it) but graphics were glitched by vertical lines :

 Looking at PCB I spotted two rows of 4164 devices which are part of the line buffer circuit:

 They are 64 x 1-bit dynamic RAMs, here's pinout :

The oscilloscope revealed floating outputs on three of them,  you can see in below picture the bad signal (stuck at undefined voltage logic level of 1.52V) compared with an healthy one :

I removed the chips :

The out-of-circuit testing confirmed they were bad :

I installed sockets and good ICs :

No more glitches on the screen :

Board 100% working and another successful repair.