Quoted from PinMonk:Take that ribbon cable off so there's a clear view of the battery holder area and shoot another picture or two (make sure you select "original size" from the dropdown menu when dragging the pictures onto the post)
Also on System 7, 7 flashes indicates Rom0 is bad. Maybe try pressing on them to see if the pins have oxidation on them?
0 - Test Passed
1 - IC13 RAM Faulty
2 - IC16 RAM Faulty
3 - IC17 ROM 2 Faulty
4 - IC17 ROM 2 Faulty
5 - IC20 ROM I Faulty
6 - IC14 Game ROM 1 Faulty
7 - IC26 Game ROM 0 Faulty
8 - IC19 CMOS RAM or memory protect circuit faulty
9 - Coin-door closed, memory protect circuit faulty, or IC19 CMOS RAM Faulty.
Not sure what System 7 error codes have to do with a System 11 MPU.