Quoted from YeOldPinPlayer:To check the ribbons, reverse all connectors on the ribbon. If the malfunction moves, the ribbon is bad.
Obviously if your ribbon is keyed you can't simply reverse it without doing something with the keyed pin.
In test mode do all three lamps flash when testing lamps 1, 2, and 3 in every column? Or only when testing lamp 1 in the column? When testing during game play with the glass off do all three inserts in the columns flash when any one of the inserts should come on?
Just to clarify (even though you did say all connectors), flip BOTH SIDES of the ribbon connector. Not just one. You want the same paths as before, just using different sides of the cable. Otherwise you will short things out and send/receive voltages where they aren't supposed to go.