1995 Buick Lesabre power antenna stuck in the up position, antenna wont go down......
 

I have a 1995 Buick Lesabre. The power radio antenna is stuck in the up position, tried turning the radio on and off several times but the antenna will not go down... not sure how to proceed... is this a common problem?
Is there a way to repair the antenna problem or do I have replace the entire mechanism? Thanks