As others have already said, almost any large format camera lens shutter is repairable. Some will not be able to be brought up to spec on all shutter speeds, but they were often not very accurate in the first place (like old Ilex shutters, for example). With very old shutters, it is also a very good idea to check what the shutter blades are made of - some are essentially blackened card stock and if you get them wet with lubricant, they'll just dissolve.