You should have the tuner "aligned". That is done by someone who knows how to repair these old units. Your other options are: try to find someone who will walk you through this as best as can be done without special equipment, which you had better be "handy" to be able to do even that, or just live with it as it is.
You might find someone willing to walk you through what you can do at audiokarma.com if no one is willing here, but be very careful if you attempt such a thing on your own. And if you screw it up, you will have no choice then but to either have it repaired professionally or just never listen to the tuner. And that is assuming you don't electrocute yourself.
My advice is to find a repair shop or live with it as is if you are too poor for that.
