Make sure the canon works properly. If you are not familiar with T2 I would watch a few videos to see how the game is supposed to function, that way you'll know what to look for during inspection. Look for a credit dot on the DMD (see picture for location of credit dot). If there is a credit dot it could mean something as simple as the time and date have not been set on the machine. It could also mean something on the machine is not functioning properly. This along with what YeOldPinPlayer mentioned should help.

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