Stuck rpm gauge..

[86lxttop]

1990 lx 5.0 140 mph cluster. The whole instrument cluster works perfectly until a few days ago, now I turn on my car and the rpm needle goes straight to 4,000 rpms and stays there. Depending on the rpms it'll goes between 4k and 5k. When I turn the car off it goes to zero. Anyone else had this problem or know how to repair it? Could possibly be a loose connection I guess but I'll have to takes cluster out to figure that out. Let me know -James