Contra Repair Logs
Symptom: Horizontal white lines on the screen
The board had horizontal white lines through all background images. Player and power ups looked normal. Checked the ROMs on the board and found the video ROM at location 7F had all outputs stuck high.
The ROM was a 2Mb mask ROM with an odd pinout. Used a 27C400 EPROM to replace it. Tied pin 1 (A17) to ground. The pin was left floating on the board since it was unused on the 2Mb ROM.
Played a game to test the board.