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Pre-show testing found a couple of issues with the multi-game PCB. Firstly, the sprites on Galaxian had colour banding across the screen that was more clearly visible on Scramble. Secondly, some of the sounds weren't working properly.
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On the bench the graphics & sound issues were still present. Starting with graphics
testing with the Arduino ICT passed all the RAM. A "RAM Write All Lo" clearly illustrated
the colour banding on the display. Using a video probe showed the banding on IC 6M (LS273)
pin 4 input (COL0). Progressing upstream to IC 2S (LS00) pin 6 output with input pin 5
high and pin 4 (RC0S) active. Moving on to the five 27LS00 sprite RAM:-
Moving on to the sounds I checked the sound triggers at IC 9L (LS259) and found them all inactive. IC 9M (LS259) outputs were toggling OK with sound activity. Since it was already in a socket I replaced IC 9L and the sounds were fixed. To be sure the socket wasn't bad I tried the IC in another position to confirm the IC was bad.
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To my surprise with the PCB installed back in the cabinet the sprites were missing colours. I pressed on the sprite RAM IC's to find that the missing colours came back with pressure. I suspected the sprite RAM sockets were bad and replaced them all. On the bench the game was running OK with no obvious mechanical problems with the sprite RAM.
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Back in the cabinet for the second attempt the game was still running OK and ran with no further issues for several hours.