That's what I figured... but I've tried re-seating everything a few times... I guess I'll keep trying this idea until I find something... i know it's something simple... i just have to figure out where the bad connection is...
I just got a VERY used 1981 Frogger upright. Worked fine in my garage, moved it inside & now all the graphics are represented by numbers (mostly 0's). According to the manual... this is a ROM issue... & it lists 4 different ROMs to check.
These ROMs are soldered onto the PCB (it appears)...