Optigan

Usually this problem can be cleared up by getting into the contact board and using a pencil eraser to “erase” all the gunk and oxidization from the contacts. This process is actually very easy- it just takes awhile to gain access to the contact board itself. Sometimes the problem remains no matter how much you manage to clean your contacts. In this case, usually you’ve got a bad photo-cell, and there’s not really anything you can do.